fixed timeline output bug and return empty timeline instead of None

Author: cato-o

src/py-opentimelineio/opentimelineio/console/otiodiff/getDiff.py

@@ -36,7 +36,7 @@ def diffTimelines(timelineA, timelineB):
 
     makeTimelineSummary(timelineA, timelineB)
 
-    outputTimeline = None
+    outputTimeline = otio.schema.Timeline()
     # process video tracks, audio tracks, or both
     if hasVideo and hasAudio:
         videoClipTable = categorizeClipsByTracks(timelineA.video_tracks(), timelineB.video_tracks())

src/py-opentimelineio/opentimelineio/console/otiotool.py

@@ -121,7 +121,7 @@ def main():
 
     if args.diff:
         # TODO? stack, concat, diff make mutually exclusive
-        diff_otio(timelines)
+        timelines = [diff_otio(timelines)]
 
     # Phase 6: Remove/Redaction
 
@@ -510,8 +510,6 @@ def read_inputs(input_paths):
         timelines.append(timeline)
     return timelines
 
-# ======= NEW =======
-
 def diff_otio(timelines):
     # TODO: check file format of timelines for OTIO
     """Return an annotated timeline showing how clips changed from the first to the second timeline"""
@@ -520,13 +518,7 @@ def diff_otio(timelines):
     if len(timelines) != 2:
         print("Warning: more than 2 timelines provided as input. Only the first two timelines will be diffed.")
     else:
-        timelines = [getDiff.diffTimelines(timelines[0], timelines[1])]
-        if len(timelines) == 0:
-            print("No output timeline generated by diff")
-
-    return timelines
-
-# ===================
+        return getDiff.diffTimelines(timelines[0], timelines[1])
 
 def keep_only_video_tracks(timeline):
     """Remove all tracks except for video tracks from a timeline."""