DeselectRow as we delete rows to avoid asserts

eeschema/dialogs/dialog_label_properties.cpp

@@ -676,6 +676,8 @@ void DIALOG_LABEL_PROPERTIES::OnDeleteField( wxCommandEvent& event )
 
     for( int row : selectedRows )
     {
+        //avoids an assert if we deselect early here
+        m_grid->DeselectRow( row );
         m_fields->erase( m_fields->begin() + row );
 
         // notify the grid