fix flatvalues for median cube measure

src/cr/cube/cube.py

@@ -1087,12 +1087,10 @@ def _flat_values(self) -> Optional[np.ndarray]:
         measure_payload = self._cube_dict["result"].get("measures", {}).get("median")
         if measure_payload is None:
             return None
-        return np.array(
-            tuple(
-                np.nan if isinstance(x, dict) else x for x in measure_payload["data"]
-            ),
-            dtype=np.float64,
-        ).flatten()
+        data = np.array(measure_payload["data"]).flatten()
+        return np.where([isinstance(x, dict) for x in data], np.nan, data).astype(
+            np.float64
+        )
 
 
 class _OverlapMeasure(_BaseMeasure):