[extractor/common] Restrict checks when auto calculating tbr

diff --git a/youtube_dl/extractor/common.py b/youtube_dl/extractor/common.py
index 33290fd7474e85ca559f5f3caa7a9aacf414e2a9..b3d57dfce100f10605287a7d086281eb2d055fe7 100644 (file)
--- a/youtube_dl/extractor/common.py
+++ b/youtube_dl/extractor/common.py
@@ -828,7 +828,7 @@ class InfoExtractor(object):
         for f in formats:
             # Automatically determine tbr when missing based on abr and vbr (improves
             # formats sorting in some cases)
-            if 'tbr' not in f and 'abr' in f and 'vbr' in f:
+            if 'tbr' not in f and f.get('abr') is not None and f.get('vbr') is not None:
                 f['tbr'] = f['abr'] + f['vbr']
 
         def _formats_key(f):