avoid crash if user asks to go back passed beginning of filelist (stay on first)
avoid crash if user asks to go back passed beginning of filelist (stay on first)

git-svn-id: https://beagle.whoi.edu/svn/ifcb/trunk@1225 9f5e5bc8-6430-4f94-ad00-aad15e9f9366

Former-commit-id: c9a3095b11a29808ad28fbfc046e43c819feaa92
hsosik/ifcb-analysis,hsosik/ifcb-analysis,hsosik/ifcb-analysis,hsosik/ifcb-analysis,hsosik/ifcb-analysis