don't collate works that haven't had metadata fetched yet

dlibrary/dlibrary.py

@@ -362,9 +362,9 @@ def collate(args):
                 work_collation_dir.rmdir()
 
         virtual = cur.execute("SELECT virtual FROM works WHERE id = ?", (work_id,)).fetchone()
-        if virtual == (1,):
+        if virtual in [(1,), None]:
             if work_id in specified_works:
-                print(f'Work {work_id} is virtual!')
+                print(f'Work {work_id} {"is virtual" if virtual == (1,) else "has no metadata"}!')
                 any_warnings = True
                 break
             continue