MySQL Bugs: #70518: Null reference exception when drawing layer under tables

Bug #70518	Null reference exception when drawing layer under tables
Submitted:	4 Oct 2013 6:27	Modified:	6 Nov 2013 22:25
Reporter:	Nikola Novak	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Workbench: Modeling	Severity:	S3 (Non-critical)
Version:	6.0.7.11215	OS:	Windows (8)
Assigned to:		CPU Architecture:	Any
Tags:	layer, model, null, undo

Description:
MySQL Workbench encounters a null reference exception when the second layer is drawn under some tables. This happens no matter how you draw the layer, as long as there are tables over it.

How to repeat:
1. Create a new model (or open existing one and continue with step 4).
2. Add a diagram.
3. In the diagram, create at least one table (empty or not, doesn't matter).
4. Draw a layer under the table so that it encompasses the table.
5. Click undo.
6. Draw another layer, again so that it encompasses the table.

After this, adding new layers results in the same error. It is possible to save the work and reload and the bug won't resurface. Any added layers after the bug happened will be black.

(Edit: Changed severity.)

Thank you for the bug report.

Exception = System.NullReferenceException
Message = Object reference not set to an instance of an object.
FullText = System.NullReferenceException: Object reference not set to an instance of an object.
   at MySQL.Forms.TreeNodeImpl.remove_from_parent(TreeNodeImpl* )
   at wb.ModelDiagramForm.handle_mouse_button(ModelDiagramForm* , MouseButton , Boolean , Int32 , Int32 , EventState )
   at MySQL.Workbench.ModelDiagramFormWrapper.OnMouseUp(MouseEventArgs e, Int32 X, Int32 Y, Keys keystate, MouseButtons buttons)
   at MySQL.GUI.Workbench.ModelDiagramForm.CanvasPanel_MouseUp(Object sender, MouseEventArgs e)
   at System.Windows.Forms.Control.OnMouseUp(MouseEventArgs e)
   at MySQL.Utilities.WindowsCanvasViewerPanel.OnMouseUp(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Fixed as of MySQL Workbench 6.0.8, and here's the changelog entry:

When creating a table on a model diagram, an unhandled NULL reference
exception was thrown when a second layer was drawn under some tables.

Thank you for the bug report.