Blender Git Loki

Fix T71995: Texture Paint workspace crash with new scene

Issue likely caused by 8b31f6fb2169.

With this, initializing the toolsystem (e.g. for a new workspace-scene
combination) would skip the entire create->initialize routine for
image/texture painting settings. Reason being that these are not
allocated, unlike other paint settings. So while correctly skipping the
create part, it also skipped the initialization, which was still needed.

This does further changes in related code to avoid NULL pointer
accesses.