identity: Fix crash when receiving a gap event outside the current segment
We were checking if the start time of the gap event was GST_CLOCK_TIME_NONE, which is superfluous because that cannot happen, and then not checking if it was NONE after gst_segment_to_running_time, which caused a crash if an identity received a gap event fully or partially outside the current segment.
This patch was done in cooperation with: Jan Alexander Steffens (heftig) jan.steffens@ltnglobal.com