Caused by rB571362642201: VSE: Improve motion-picture workflow where versioning code for new sequencer tool
settings was only done for scenes already having sequencer scene->ed.

If scene->ed was not present, sequencer tool settings were never
initalized for this scene [if the VSE was then used later], leading to
crashes in some places.

Now just use the versioning code to initalize sequencer tool settings
for all scenes not having them yet.