add error message

pyopensprinkler/program.py

@@ -112,7 +112,7 @@ def _encode_offset_minutes(self, offset_type, start_time_offset):
             return start_time_offset
 
     def _get_offset_type(self, start_times, start_index):
-        """Get start time offset type ('midnight', 'sunset', or 'sunrise')"""
+        """Get start time offset type ('disabled', 'midnight', 'sunset', or 'sunrise')"""
         use_sunset = bool(self._is_set(start_times[start_index], START_TIME_SUNSET_BIT))
         use_sunrise = bool(
             self._is_set(start_times[start_index], START_TIME_SUNRISE_BIT)
@@ -250,11 +250,14 @@ async def set_program_start_time_offset(self, start_index, start_time_offset):
                 f"cannot update start{start_index} with minutes when start time type is 'repeating'"
             )
 
-        if ():
-            raise ValueError(f"cannot adjust offset when start{start_index} is Disabled")
-
         dlist = self._get_program_data().copy()
         current_offset_type = self._get_offset_type(dlist[3], start_index)
+
+        if (current_offset_type == "disabled"):
+            raise ValueError(
+                f"cannot adjust offset when start{start_index} is Disabled"
+            )
+
         new_start = self._encode_offset_minutes(current_offset_type, start_time_offset)
         dlist[3][start_index] = new_start
         params = self._format_program_data(dlist)