Ensure basesPerGraph is an int when rezooming
Ensure basesPerGraph is an int when rezooming

re #983

victor-lin/npact,NProfileAnalysisComputationalTool/npact,victor-lin/npact,NProfileAnalysisComputationalTool/npact,victor-lin/npact,victor-lin/npact,NProfileAnalysisComputationalTool/npact,NProfileAnalysisComputationalTool/npact,victor-lin/npact,NProfileAnalysisComputationalTool/npact