small fixes

catalog.py

@@ -197,6 +197,8 @@ def _parse_frame(frame: numpy.ndarray, for_sale: bool) -> Iterator[numpy.ndarray
     # Last line has dashes after but first line doesn't have dashes before,
     # therefore we prepend the list with zero for the starting line.
     y_lines = list((frame[:, 0] < 200).nonzero()[0])
+    if not y_lines:
+        return
 
     # Normalize row lines by taking the average of all of them.
     # We know they are 53.45px apart, so we find the best offset from given lines.

scanner.py

@@ -40,7 +40,7 @@ def scan_media(filename: str, mode: str = 'auto', locale: str = 'auto', for_sale
     if mode not in SCANNERS:
         raise RuntimeError('Invalid mode: %r' % mode)
 
-    assert mode != 'storage', 'Storage scanning is not yet supported.'
+    assert mode != 'storage', 'Storage scanning is not supported.'
 
     kwargs = {}
     if mode == 'catalog':

storage.py

@@ -112,7 +112,7 @@ def _is_duplicate_row(all_rows: List[numpy.ndarray], new_row: List[numpy.ndarray
         return False
 
     new_concat = cv2.hconcat(new_row)
-    # Checks the last 3 rows for similarities to the newly added row.
+    # Checks the last 4 rows for similarities to the newly added row.
     for ind in [slice(-8, None), slice(-16, -8), slice(-24, -16), slice(-32, -24)]:
         old_concat = cv2.hconcat(all_rows[ind])
         if old_concat is None: