fix typo

nxtomomill/converter/hdf5/acquisition/standardacquisition.py

@@ -595,9 +595,9 @@ class StandardAcquisition(BaseAcquisition):
             unit = "m"
         else:
             distance, unit = self._get_distance()
-            if distance is not None:
-                detector_node["distance"] = distance
-                detector_node["distance"].attrs["unit"] = unit
+        if distance is not None:
+            detector_node["distance"] = distance
+            detector_node["distance"].attrs["unit"] = unit
         # write x and y pixel size
         # if magnified pixel size is found then we right this value.
         # otherwise will take pixel size (if found)