Set reference chip to the first available member if chip #3 is missing from a WFPC2 observation.
Set reference chip to the first available member if chip #3 is missing from a WFPC2 observation.

git-svn-id: e4aa3cfa51ba591d1cd1dbbaf7e4a2c2b5d7a7ff@1195 fe389314-cf27-0410-b35b-8c050e845b92

spacetelescope/stsci.tools