Merge pull request #430 in CASA/casa6 from CAS-12741 to master
* commit '096c04ea4cfdaaff0e7aefe50d31ed94dd646bb1':
pick up viewer wheel (CAS-12741)
prevent crash with 'Zoom out to Entire Image' with unzooomed image (CAS-12741)
prevent crash with 'Zoom out to Entire Image' with unzooomed image (CAS-12741)