[npr] Make SMIL extraction non-fatal (#2099)

Closes #1934
Authored by: r5d

yt_dlp/extractor/common.py

@@ -2332,7 +2332,7 @@ class InfoExtractor(object):
 
         if smil is False:
             assert not fatal
-            return []
+            return [], {}
 
         namespace = self._parse_smil_namespace(smil)
 

yt_dlp/extractor/npr.py

@@ -91,7 +91,8 @@ class NprIE(InfoExtractor):
                     elif format_id == 'smil':
                         smil_formats = self._extract_smil_formats(
                             format_url, media_id, transform_source=lambda s: s.replace(
-                                'rtmp://flash.npr.org/ondemand/', 'https://ondemand.npr.org/'))
+                                'rtmp://flash.npr.org/ondemand/', 'https://ondemand.npr.org/'),
+                            fatal=False)
                         self._check_formats(smil_formats, media_id)
                         formats.extend(smil_formats)
                     else: