Description of problem:
The form modeller window will on occasions appear very small whenever the user switches from the authoring perspective to another one (for example the Tasks perspective), and the switches back to authoring.

Version-Release number of selected component (if applicable):

Steps to Reproduce:

1. Open a form in the authoring perspective
2. Switch to the task perspective
3. Switch back to the authoring perspective
4. Select the editor with the previously opened form (if not already visualized)

Actual results:
The form modeller should now appear only to fill about 1/3rd of the available vertical space, leaving the rest (until the problems view) empty. See attached screenshot.

Expected results:
Should fill all the available space up to the problems view

Additional info: