fix: refuse an archive holding no declared member

_holding_members kept every same-named copy when the best held nothing,
so galgames.zip, a lone assembler listing, resolved by name for mame,
groovymame and mame4droid-2024, and awbios.zip for mame4droid. Such a
copy now resolves as hash_mismatch.

mame2003_plus declared its contents by name only, while fileio.c:1031-1040
loads a member by CRC when the name is absent. The 61 members now carry
the CRC their driver declares, so stvbios, megatech and the six ZN sets
keep matching the archives the collection holds.

scripts/common.py

@@ -1094,6 +1094,10 @@ def _holding_members(paths: list[str], members: list[dict]) -> list[str]:
 
     scores = {path: held(path) for path in paths}
     best = max(scores.values(), default=(0, 0))
+    if best == (0, 0):
+        # Not one declared member in any copy: the name is all that matches,
+        # and galgames.zip holding only an assembler listing is not the set.
+        return []
     return [path for path in paths if scores[path] == best]