When drawing on a frame that didn't have a keyframe, but did have a drawing,
Blender would report that there was no drawing to draw on.
The issue was some faulty logic on the invoke of the drawing code.
Now, this properly checks if a new frame needs to be inserted and
only reports an error in case auto-key is off and there is no drawing.
Pull Request: https://projects.blender.org/blender/blender/pulls/116417
da78dd47e3