An element with command line tool can be put to the scene right after its removing from the palette in Workflow Designer

Scenario:

1. Open the Workflow Designer.
2. Create an element with command line tool.
3. Open the "Elements" tab on the palette.
4. Click on the created element on the palette with the left mouse button. Do not release the button.
5. Click on the created element on the palette with the right mouse button. The right mouse button can be released immediately, the left mouse button is still pressed.
   Expected result: a context menu is shown.
6. Release the left mouse button. The mouse shouldn't be moved during all these clicking.
7. Select the "Remove" menu item.
   Expected result: the element is removed from the palette.
8. Click somewhere on the scene with the left mouse button.
   Current result: an instance of the removed element is added to the scene.
   Expected result: nothing happens.