Identify poor vfat data in S-curve analysis
Description
The S-curve analysis version developed on !47 (merged) can identify when a VFAT just has zeros and label it as an empty vfat. But, there are some cases where vfat is not completely powered off but neither has good detections (like in the images). It should be necessary to identify and label them (maybe to mask them). Probably those cases are responsible to produce the warning message OptimizeWarning: Covariance of the parameters could not be estimated
which at the moment is being ignored.
Possible fixes
I think that some callback produced by the warning message could be used to identify problematic VFATs or channels. Another option could be, to think if it would be possible to use the new histogram added in the S-curves ROOT file producer (the number of events per point) to catch such cases.