When grabbing a merged channel part with a time window that extends beyond midnight, programs that start before midnight get an end time equal to the window end time if the grabber does not provide an end time.
Reported by Johnzered

h4. Steps to Reproduce
In WebEPG, map a channel to 2 grabbers (merged channel) so that one of them has a time window that crosses midnight (e.g. 20:00 to 05:30). Choose grabbers that do not grab the program end time.
Do a grab and notice that programs starting before midnight but within the above time window all get an end time equal to the end of the time window (i.e. 05:30 in the above case).