Fix download filename with invalid headers (bug 1440)

Merged from the 'tres' branch.

src/gpodder/download.py

@@ -746,7 +746,9 @@ def run(self):
             disposition_filename = get_header_param(headers, \
                     'filename', 'content-disposition')
 
-            if disposition_filename is not None:
+            # Some servers do send the content-disposition header, but provide
+            # an empty filename, resulting in an empty string here (bug 1440)
+            if disposition_filename is not None and disposition_filename != '':
                 # The server specifies a download filename - try to use it
                 disposition_filename = os.path.basename(disposition_filename)
                 self.filename = self.__episode.local_filename(create=True, \

src/gpodder/model.py

@@ -1017,6 +1017,12 @@ def local_filename(self, create, force_update=False, check_only=False,
                 return os.path.join(self.channel.save_dir, self.filename)
 
         if self.filename is None or force_update or (self.auto_filename and self.filename == urldigest+ext):
+            # Avoid and catch gPodder bug 1440 and similar situations
+            if template == '':
+                log('Empty template. Report this podcast URL %s',
+                        self.channel.url)
+                template = None
+
             # Try to find a new filename for the current file
             if template is not None:
                 # If template is specified, trust the template's extension