fix empty string case in _coerce_extensions

DeepLabCut · MMathisLab · May 15, 2026 · May 4, 2026 · May 4, 2026 · May 7, 2026
commit 39cfd94311191f2327c3789d0b5c85392d1d85e0
diff --git a/deeplabcut/utils/auxfun_videos.py b/deeplabcut/utils/auxfun_videos.py
@@ -691,7 +691,7 @@ def _coerce_extensions(extensions: str | Sequence[str] | None) -> set[str] | Non
         # NOTE @deruyter92: support legacy API, which mixed strings and iterables.
         if isinstance(extensions, (list, tuple, set)):
             explicit_suffixes = {f".{e.lstrip('.').lower()}" for e in extensions}
-        elif isinstance(extensions, str):
+        elif isinstance(extensions, str) and not extensions == "":
             explicit_suffixes = {f".{extensions.lstrip('.').lower()}"}
         else:
             explicit_suffixes = None