Pull Request for Issue1098 - REIXS crash on load XES scans

can't call ```computeCachedValues()``` until there's a valid ```inputSource_```

```onAnalysisBlockInputDataSourcesChanged()``` needs to handle ```curve2Disable()``` properly, and can't rely on ```onCurve2DisabledCheckBoxChanged()``` on db load since it checks for a change before doing anything.