Merge pull request #567 from Ragora/bugfix-guieditor-mission-editor

* BugFix: Correct an error where the GUI editor cannot be opened

Templates/BaseGame/game/tools/guiEditor/scripts/guiEditor.ed.tscript

@@ -121,6 +121,8 @@ function GuiEditor::close(%this)
    if(Canvas.getContent() != GuiEditorGui.getId())
       return;
 
+   $InGuiEditor = false;
+
    GuiGroup.add(GuiEditorGui);
    
    Canvas.setContent(GuiEditor.lastContent);