rtponviftimestamp: Fix drop-out-of-segment=false mode
Fixing unexpected buffer dropping and flow error in case that:
- use-reference-timestamps=false
- drop-out-of-segment=false
- Calculated utc offset is not valid because buffer is out-of-segment
The above case should be considered as a valid data flow without returning errors.
Fixing regression introduced by !1683 (merged)
Edited by Seungha Yang