Merge pull request #47 from sall/master

Merge from sall/vixen
Hacked fix for the Multiple Form Opening issue... When closing forms, objects were disposed of as they should be, but when additional sequences were later opened, the objects were somehow reused, and since the objects had been disposed an ObjectDisposedException was thrown and caused the user to just wait indefinately
Merge branch 'master' of https://github.com/gizmohd/vixen.git
Prevent editor from exploding when loading a new sequence
Better fix... remove event handlers to prevent form exploding on reload
Add some null reference checking to the GDI rendering in the preview. For some reason, my window was displaying as a 0x0 window, so it couldn't get a visible graphics object to operate on, and would crash without me being able to fix it up.
3.0.8r2 changes (trivial).