Fix case where mdata_const may be undefined

src/cal_tools/tools.py

@@ -398,7 +398,7 @@ def get_pdu_from_db(karabo_id: str, karabo_da: Union[str, list],
 
     :param karabo_id: Karabo identifier.
     :param karabo_da: Karabo data aggregator.
-    :param constant: Calibration constant object to 
+    :param constant: Calibration constant object to
                      intialize CalibrationConstantMetadata class.
     :param condition: Detector condition object to
                       intialize CalibrationConstantMetadata class.
@@ -548,8 +548,8 @@ def get_from_db(karabo_id: str, karabo_da: str,
                     raise RuntimeError(f'{e}')
 
         if ntries > 0:
+            mdata_const = metadata.calibration_constant_version
             if load_data and meta_only:
-                mdata_const = metadata.calibration_constant_version
                 fpath = Path(mdata_const.hdf5path, mdata_const.filename)
                 with h5py.File(fpath, "r") as f:
                     arr = f[f"{mdata_const.h5path}/data"][()]