Bug fix and variable name changing

[Li-Jiaoyang97]

Hi, in this PR, I have modified two files:

• In Selection/AnalysisTools/FlashMatching_tool.cc: I added __flashmatch to the flash-related variable names since these name can also be found in Selection/AnalysisTools/PMTWaveform_tool.cc; Please let me know if you want to do it differently.
• In Selection/AnalysisTools/PMTWaveform_tool.cc, I fixed the if-condition, see the line 207, which preventing the calibrated PE being filled.