crash during concurrent tasks

[rwhuibrex]

Large library 28k tracks, when running a muliple track 'level volume' command, then execute a block of Auto Organize across at least some of these tracks.

When the system runs into a track that is being leveled and moved to a new location concurrently, it crashes.

MM should know better and wait for a pending action to complete before moving the target track.

Happens consistently.