IGN:...

src/calibre/ebooks/metadata/__init__.py

@@ -207,9 +207,9 @@ class MetaInformation(object):
             title = mi.title
             authors = mi.authors
         self.title = title
-        self.author = list(authors) # Needed for backward compatibility
+        self.author = list(authors) if authors else []# Needed for backward compatibility
         #: List of strings or []
-        self.authors = list(authors)
+        self.authors = list(authors) if authors else []
         self.tags = getattr(mi, 'tags', [])
         #: mi.cover_data = (ext, data)
         self.cover_data   = getattr(mi, 'cover_data', (None, None))

src/calibre/library/cli.py

@@ -15,6 +15,7 @@ from calibre import terminal_controller, preferred_encoding
 from calibre.utils.config import OptionParser, prefs
 try:
     from calibre.utils.single_qt_application import send_message
+    send_message
 except:
     send_message = None
 from calibre.ebooks.metadata.meta import get_metadata

src/calibre/library/database2.py

@@ -622,11 +622,7 @@ class LibraryDatabase2(LibraryDatabase):
         if title:
             if not isinstance(title, unicode):
                 title = title.decode(preferred_encoding, 'replace')
-            tf = FIELD_MAP['title']
-            q = title.lower()
-            for record in self.data._data:
-                if record is not None and record[tf].lower() == q:
-                    return True
+            return bool(self.conn.get('SELECT id FROM books where title=?', (title,), all=False))
         return False
 
     def has_cover(self, index, index_is_id=False):