Bug: Activity backups with missing libraries break activity and course backup/restore

[danowar2k]

Situation:

• Backup an activity on site A, which has h5p library LIB X.Y
• Restore the activity on site B, which has LIB X.Y not installed
• End up with a broken HVP activity
  • Can't be viewed
  • Can't be backed up and restored
  • Complete course doesn't work anymore

This of course only happens if you have set the old site to not backup H5P libraries (which one has to do often, because the library backup process takes ages).

Better would be if the above restore leads to a cancelled backup with a clear message that HVP activity called "NAME" couldn't be restored because library LIB X.Y is missing on the site.

Also helpful would be to be able to install older library versions....