Merge pull request #871 in CASA/casa from CAS-11734 to master
* commit 'd5d125e306416d53d1a0ca504acddf514ca854eb':
Fix compiler warning
Adds unit tests that checks the phantom SPWs are treated correctly by getChannels()
Fix typo and simplify logic
Support calling getChannels() for "phantom" SPWs
Revert "Workaround issue with CAS-11734: getChannels() throws if phantom SPWs are present"