Fix server crash when there is no entry

Return samples as an empty list when geomean is None.


git-svn-id: https://llvm.org/svn/llvm-project/lnt/trunk@211580 91177308-0d34-0410-b5e6-96231b3b80d8
Fix geomean calculation for previous run


git-svn-id: https://llvm.org/svn/llvm-project/lnt/trunk@211582 91177308-0d34-0410-b5e6-96231b3b80d8