Fix DatabaseError: no such table: moz_favicons

Tested with

System1, has moz_favicons
Firefox 57.0.2
Windows 10.0.16299

System2, does not have moz_favicons
Ubuntu 16.04.03
Firefox/57.0

Closes #261

Closes #251

Also related
- https://www.bleachbit.org/forum/firefox-55
- https://bugs.launchpad.net/linuxmint/+bug/1738086

bleachbit/Special.py

@@ -260,8 +260,9 @@ def delete_mozilla_url_history(path):
     fav_suffix = "where id not in (select favicon_id " \
         "from moz_places where favicon_id is not null ); "
 
-    cols = ('url', 'data')
-    cmds += __shred_sqlite_char_columns('moz_favicons', cols, fav_suffix)
+    if __sqlite_table_exists(path, 'moz_favicons'):
+        cols = ('url', 'data')
+        cmds += __shred_sqlite_char_columns('moz_favicons', cols, fav_suffix)
 
     # delete any orphaned history visits
     cmds += "delete from moz_historyvisits where place_id not " \