Add parentheses to the NULL_TERMINATE macro found in many samples

Put parentheses around the parameter concerning the NULL_TERMINATE macro. This macro is found in many samples.

Instead of: #define NULL_TERMINATE(buf) buf[(sizeof(buf) / sizeof(buf[0])) - 1] = '\0'

we need to change to macro to #define NULL_TERMINATE(buf) (buf)[(sizeof((buf)) / sizeof((buf)[0])) - 1] = '\0'