Let ctuples not automatically infer to PyObject

Cython/Compiler/TypeInference.py

@@ -584,6 +584,10 @@ def safe_spanning_type(types, might_overflow, pos, scope):
         # used, won't arise in pure Python, and there shouldn't be side
         # effects, so I'm declaring this safe.
         return result_type
+    elif resolved_result_type.is_ctuple:
+        # Since structs are considered safe, and ctuples are essentially structs
+        # with tuple-like syntax, they should be safe for the same reasons.
+        return result_type
     # TODO: double complex should be OK as well, but we need
     # to make sure everything is supported.
     elif (resolved_result_type.is_int or resolved_result_type.is_enum) and not might_overflow: