Handle null timestamp or runtime TvMaze fields

In rare cases, the TvMaze database provides null timestamp
or runtime data fields. To make the metadata retrieval script
more fault tolerant, null checks have been added for these values.

When the timestamp field is null, don't use it to generate a
datetime to use in a search for a matching episode.

When the runtime duration field is null, the delta size is
now set to zero minutes. The code which looks for an episode
match has been updated to separate "on time" recordings from
"a little late" recordings to accommodate the possible delta
size of zero.

Refs: MythTV#654

mythtv/programs/scripts/metadata/Television/tvmaze.py

@@ -244,31 +244,43 @@ def buildNumbers(args, opts):
             early_match_list = []
             minTimeDelta = timedelta(minutes=60)
             for i, ep in enumerate(episodes):
-                epInTgtZone = datetime.fromIso(ep.timestamp, tz = posixtzinfo(show_tz))
-                durationDelta = timedelta(minutes=ep.duration)
-
-                # Consider it a match if the recording starts late, but within the duration of the show.
-                if epInTgtZone <= dtInTgtZone < epInTgtZone+durationDelta:
-                    # Recording start time is within the range of this episode
-                    if opts.debug:
-                        print('Recording in range of inetref %d, season %d, episode %d (%s ... %s)' \
-                                % (inetref, ep.season, ep.number, epInTgtZone, epInTgtZone+durationDelta))
-                    time_match_list.append(i)
-                    minTimeDelta = timedelta(minutes=0)
-                # Consider it a match if the recording is a little bit early. This helps cases
-                # where you set up a rule to record, at say 9:00, and the broadcaster uses a
-                # slightly odd start time, like 9:05.
-                elif epInTgtZone-minTimeDelta <= dtInTgtZone < epInTgtZone:
-                    # Recording started earlier than this episode, so see if it's the closest match
-                    if epInTgtZone - dtInTgtZone == minTimeDelta:
+                if ep.timestamp:
+                    epInTgtZone = datetime.fromIso(ep.timestamp, tz = posixtzinfo(show_tz))
+                    if ep.duration:
+                        durationDelta = timedelta(minutes=ep.duration)
+                    else:
+                        durationDelta = timedelta(minutes=0)
+
+                    if epInTgtZone == dtInTgtZone:
                         if opts.debug:
-                            print('adding episode to closest list', epInTgtZone - dtInTgtZone, '\n')
-                        early_match_list.append(i)
-                    elif epInTgtZone - dtInTgtZone < minTimeDelta:
+                            print('Recording matches inetref %d, season %d, episode %d at %s' \
+                                % (inetref, ep.season, ep.number, epInTgtZone))
+                        time_match_list.append(i)
+                        minTimeDelta = timedelta(minutes=0)
+
+                    # Consider it a match if the recording starts late,
+                    # but within the duration of the show.
+                    elif epInTgtZone < dtInTgtZone < epInTgtZone+durationDelta:
+                        # Recording start time is within the range of this episode
                         if opts.debug:
-                            print('this episode is new closest', epInTgtZone - dtInTgtZone, '\n')
-                        minTimeDelta = epInTgtZone - dtInTgtZone
-                        early_match_list = [i]
+                            print('Recording in range of inetref %d, season %d, episode %d (%s ... %s)' \
+                                % (inetref, ep.season, ep.number, epInTgtZone, epInTgtZone+durationDelta))
+                        time_match_list.append(i)
+                        minTimeDelta = timedelta(minutes=0)
+                    # Consider it a match if the recording is a little bit early. This helps cases
+                    # where you set up a rule to record, at say 9:00, and the broadcaster uses a
+                    # slightly odd start time, like 9:05.
+                    elif epInTgtZone-minTimeDelta <= dtInTgtZone < epInTgtZone:
+                        # Recording started earlier than this episode, so see if it's the closest match
+                        if epInTgtZone - dtInTgtZone == minTimeDelta:
+                            if opts.debug:
+                                print('adding episode to closest list', epInTgtZone - dtInTgtZone, '\n')
+                            early_match_list.append(i)
+                        elif epInTgtZone - dtInTgtZone < minTimeDelta:
+                            if opts.debug:
+                                print('this episode is new closest', epInTgtZone - dtInTgtZone, '\n')
+                            minTimeDelta = epInTgtZone - dtInTgtZone
+                            early_match_list = [i]
 
             if not time_match_list:
                 # No exact matches found, so use the list of the closest episode(s)