Do not confuse code analyzers with out-of-bounds array access look alike

The code is only getting the address, but we might be performing an
addressing that is out-of-bounds. Avoid it and use the address form
instead.

Warned-by: cppcheck (objectIndex)

src/setproctitle.c

@@ -284,7 +284,7 @@ setproctitle_impl(const char *fmt, ...)
 
 	if (nul < SPT.nul) {
 		*SPT.nul = '.';
-	} else if (nul == SPT.nul && &nul[1] < SPT.end) {
+	} else if (nul == SPT.nul && (nul + 1) < SPT.end) {
 		*SPT.nul = ' ';
 		*++nul = '\0';
 	}