Post #677: 
roaoao:
Blender’s pop-up issue. In this case you need to replace bpy.context or C with bl_context (Property or Custom tab).
Another Blender’s issue. If you check the path in Property tab you will see something like this:
bpy.data.screens["Default"].(null) ...Which means that Blender can’t generate correct path for the button. You have to find it manually.
In this case you need to use this path in Property tab:bl_context.space_data.fx_settings.use_ssaoI’ll try to fix both issues in Blender 2.79
Thank you :o