Cluster: fix segfault if pixel charge negative
This is a follow-up on !433 (merged)
After !433 (merged):
If pixel charge negative, getSeedPixel()
would return a nullptr
. This caused a seg fault in Clustering4D
.
A negative pixel charge should not occur generally. But e.g. after applying the toa/tot calibration to the Timepix3, it happens occationally.