Fix saving channel preferences overwrite default row status

ALTER TABLE ChannelPrefer RENAME COLUMN "DEFAULT" to "isDefault";

Closes #280 (closed)

Also update a default row check to not rely on a hard-coded value.

sohstationviewer/view/channel_prefer_dialog.py

@@ -508,9 +508,13 @@ class ChannelPreferDialog(OneWindowAtATimeDialog):
         """
         selected_row_idx = self.soh_list_table_widget.indexFromItem(
             self.soh_list_item
+        ).row()
+        row_edit_button = self.soh_list_table_widget.cellWidget(
+            selected_row_idx, COL['edit']
         )
-        # Hardcoding the check for default row because there is no time.
-        if selected_row_idx.row() < 4:
+        is_default_row = not row_edit_button.isEnabled()
+
+        if is_default_row:
             err_msg = ('The selected row is a default row and cannot be '
                        'overwritten. Please select a non-default row and try '
                        'again.')