Fixes following ubdefined-behavior as reported by clang version 10.0.0-4ubuntu1~18.04.2: delta.c:139:52: runtime error: member access within null pointer of type 'struct uci_element' SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior delta.c:139:52 Signed-off-by: Petr Štetiar <ynezz@true.cz>master