[Coverity 1665807] Same on both sides in preferences_widgets.cpp

This is often the result of a copy and paste error. It may result in the operator always evaluating to the same result.

In KeySelectorControl::​tableContextMenuEvent(QWidget *, QContextMenuEvent *): The same expression occurs on both sides of an operator. (CWE-1025)

1556        case ACTION_COL:
1557            empty = (item->normal.keys.isEmpty() && item->global.keys.isEmpty());
      
CID 1665807: (#1 of 1): Same on both sides (CONSTANT_EXPRESSION_RESULT)
pointless_expression: The expression item->normal.matches_default && item->normal.matches_default does not accomplish anything because it evaluates to either of its identical operands, item->normal.matches_default.
       Did you intend the operands to be different?
1558            matches_default = (item->normal.matches_default && item->normal.matches_default);