For #26218 - Fixed various initialisation issues.
Found and fixed a few edge cases that would throw 'PythonObject is not
attached to a node' errors in Nuke, resulting in the app not being
loaded and the script being left in an error'd state.
For #26355 - Fixed width & height updating in the render path.
- Also fixed use of nuke.scriptName() for versions of Nuke before 8
- Closes #9