Close button doesn't work

[Madalin2009]

addEventHandler("onClientResourceStart",resourceRoot, 
    function() 
        GUIEditor_TabPanel = {} 
        GUIEditor_Tab = {} 
        GUIEditor_Memo = {} 
        GUIEditor_Image = {} 
  
        MTAWelcome_Window = guiCreateWindow(279,145,717,624,"Welcome to Multi Theft Awesome [v0.01]",false) 
        guiSetAlpha(MTAWelcome_Window,0.80000001192093) 
        GUIEditor_TabPanel[1] = guiCreateTabPanel(13,25,684,558,false,MTAWelcome_Window) 
        WelcomeTab = guiCreateTab("Welcome",GUIEditor_TabPanel[1]) 
        WelcomeTab_Image1 = guiCreateStaticImage(3,6,674,132,"images/logo.png",false,WelcomeTab) 
        WelcomeTab_Image2 = guiCreateStaticImage(0,104,408,207,"images/admhelp.png",false,WelcomeTab) 
        GUIEditor_TabPanel[2] = guiCreateTabPanel(395,125,272,151,false,WelcomeTab) 
        WelcomeTab_DevelopersTab = guiCreateTab("Developers",GUIEditor_TabPanel[2]) 
        DevTab_Memo = guiCreateMemo(6,8,259,110,"TheBetaFox - Owner, scripter, mapper",false,WelcomeTab_DevelopersTab) 
        guiMemoSetReadOnly(DevTab_Memo,true) 
        WelcomeTab_AdminTab = guiCreateTab("Admins",GUIEditor_TabPanel[2]) 
        AdmTab_Memo = guiCreateMemo(7,8,258,112,"WindHedgehog - Administrator\nMorrowind3 - Administrator",false,WelcomeTab_AdminTab) 
        guiMemoSetReadOnly(AdmTab_Memo,true) 
        WelcomeTab_ModTab = guiCreateTab("Moderators",GUIEditor_TabPanel[2]) 
        ModTab_Memo = guiCreateMemo(4,5,262,118,"Mr. Placeholder - Head moderator\nMrs. Wtfhax - Moderator",false,WelcomeTab_ModTab) 
        guiMemoSetReadOnly(ModTab_Memo,true) 
        GUIEditor_TabPanel[3] = guiCreateTabPanel(42,336,254,125,false,WelcomeTab) 
        GUIEditor_Tab[1] = guiCreateTab("General Help",GUIEditor_TabPanel[3]) 
        GUIEditor_Memo[1] = guiCreateMemo(5,5,244,115,"See these commands for help:\n\n/help - shows a list of commands.\n/teles - shows a list of teleports.",false,GUIEditor_Tab[1]) 
        GUIEditor_Image[1] = guiCreateStaticImage(314,296,370,200,"images/genhelp.png",false,WelcomeTab) 
        InfoTab = guiCreateTab("Information/Credits",GUIEditor_TabPanel[1]) 
        InfoTab_Image0 = guiCreateStaticImage(13,12,668,131,"images/logo.png",false,InfoTab) 
        Infotab_Image1 = guiCreateStaticImage(111,78,349,178,"images/credhelp.png",false,InfoTab) 
        GUIEditor_Memo[2] = guiCreateMemo(23,248,635,260,"Credits go to the following people:\n\n\nDevelopers & Admins:\n TheBetaFox\n\nIdeagivers:\n Inku, Morrowind3, WindHedgehog\n\nInspiration:\n [sFSE]luggi, Mave, Zezombia, Andre, robhol, Gamesnert, Morrowind3, WindHedgehog, Inku, MaykoX",false,InfoTab) 
        MTAWelcomeWindow_Progress = guiCreateProgressBar(10,585,647,30,false,MTAWelcome_Window) 
        guiProgressBarSetProgress(MTAWelcomeWindow_Progress,15) 
        MTA_WelcomeWindow_Close = guiCreateButton(659,584,39,31,"X",false,MTAWelcome_Window) 
        guiSetFont(MTA_WelcomeWindow_Close,"default-bold-small") 
        guiSetVisible(MTAWelcome_Window, true) 
        showCursor(true) 
        guiSetInputEnabled(true) 
    end 
) 
function closeWindow() 
    guiSetVisible(MTAWelcome_Window, false) 
    showCursor(false) 
    guiSetInputEnabled(false) 
end 
addEventHandler ( "onClientGUIClick", MTA_WelcomeWindow_Close, closeWindow) 

I made this GUI in the GUI Editor, and then tried to make the close button work, but it still doesn't. What's the problem?

[JR10]

addEventHandler("onClientResourceStart",resourceRoot, 
    function() 
        GUIEditor_TabPanel = {} 
        GUIEditor_Tab = {} 
        GUIEditor_Memo = {} 
        GUIEditor_Image = {} 
  
        MTAWelcome_Window = guiCreateWindow(279,145,717,624,"Welcome to Multi Theft Awesome [v0.01]",false) 
        guiSetAlpha(MTAWelcome_Window,0.80000001192093) 
        GUIEditor_TabPanel[1] = guiCreateTabPanel(13,25,684,558,false,MTAWelcome_Window) 
        WelcomeTab = guiCreateTab("Welcome",GUIEditor_TabPanel[1]) 
        WelcomeTab_Image1 = guiCreateStaticImage(3,6,674,132,"images/logo.png",false,WelcomeTab) 
        WelcomeTab_Image2 = guiCreateStaticImage(0,104,408,207,"images/admhelp.png",false,WelcomeTab) 
        GUIEditor_TabPanel[2] = guiCreateTabPanel(395,125,272,151,false,WelcomeTab) 
        WelcomeTab_DevelopersTab = guiCreateTab("Developers",GUIEditor_TabPanel[2]) 
        DevTab_Memo = guiCreateMemo(6,8,259,110,"TheBetaFox - Owner, scripter, mapper",false,WelcomeTab_DevelopersTab) 
        guiMemoSetReadOnly(DevTab_Memo,true) 
        WelcomeTab_AdminTab = guiCreateTab("Admins",GUIEditor_TabPanel[2]) 
        AdmTab_Memo = guiCreateMemo(7,8,258,112,"WindHedgehog - Administrator\nMorrowind3 - Administrator",false,WelcomeTab_AdminTab) 
        guiMemoSetReadOnly(AdmTab_Memo,true) 
        WelcomeTab_ModTab = guiCreateTab("Moderators",GUIEditor_TabPanel[2]) 
        ModTab_Memo = guiCreateMemo(4,5,262,118,"Mr. Placeholder - Head moderator\nMrs. Wtfhax - Moderator",false,WelcomeTab_ModTab) 
        guiMemoSetReadOnly(ModTab_Memo,true) 
        GUIEditor_TabPanel[3] = guiCreateTabPanel(42,336,254,125,false,WelcomeTab) 
        GUIEditor_Tab[1] = guiCreateTab("General Help",GUIEditor_TabPanel[3]) 
        GUIEditor_Memo[1] = guiCreateMemo(5,5,244,115,"See these commands for help:\n\n/help - shows a list of commands.\n/teles - shows a list of teleports.",false,GUIEditor_Tab[1]) 
        GUIEditor_Image[1] = guiCreateStaticImage(314,296,370,200,"images/genhelp.png",false,WelcomeTab) 
        InfoTab = guiCreateTab("Information/Credits",GUIEditor_TabPanel[1]) 
        InfoTab_Image0 = guiCreateStaticImage(13,12,668,131,"images/logo.png",false,InfoTab) 
        Infotab_Image1 = guiCreateStaticImage(111,78,349,178,"images/credhelp.png",false,InfoTab) 
        GUIEditor_Memo[2] = guiCreateMemo(23,248,635,260,"Credits go to the following people:\n\n\nDevelopers & Admins:\n TheBetaFox\n\nIdeagivers:\n Inku, Morrowind3, WindHedgehog\n\nInspiration:\n [sFSE]luggi, Mave, Zezombia, Andre, robhol, Gamesnert, Morrowind3, WindHedgehog, Inku, MaykoX",false,InfoTab) 
        MTAWelcomeWindow_Progress = guiCreateProgressBar(10,585,647,30,false,MTAWelcome_Window) 
        guiProgressBarSetProgress(MTAWelcomeWindow_Progress,15) 
        MTA_WelcomeWindow_Close = guiCreateButton(659,584,39,31,"X",false,MTAWelcome_Window) 
       addEventHandler ( "onClientGUIClick", MTA_WelcomeWindow_Close, closeWindow) 
        guiSetFont(MTA_WelcomeWindow_Close,"default-bold-small") 
        guiSetVisible(MTAWelcome_Window, true) 
        showCursor(true) 
        guiSetInputEnabled(true) 
    end 
) 
function closeWindow() 
    guiSetVisible(MTAWelcome_Window, false) 
    showCursor(false) 
    guiSetInputEnabled(false) 
end