html ui: do nto fail of unique id in loaded file is empty

dataloggerui/htmlui.py

@@ -115,11 +115,10 @@ def load_config_file(fname):
                     if k in config_file_dict}
 
     # Make sure device name is str and conserve unique id
-    if isinstance(formdict['device_name'], int):
-        hexname = f"{formdict['device_name']:#026X}"
-        formdict['device_name'] = hexname.replace('X', 'x', 1)
-    hexid = f"{formdict['unique_id']:#026X}"
-    formdict['unique_id'] = hexid.replace('X', 'x', 1)
+    for field in ('device_name', 'unique_id'):
+        if isinstance(formdict[field], int):
+            hexfield = f"{formdict[field]:#026X}"
+            formdict[field] = hexfield.replace('X', 'x', 1)
 
     # mV to V
     formdict['battery_cell_voltage'] = float(formdict['battery_cell_voltage']) * 1e-3