Update event_tagging.c

In function decode_tag_internal 
static int decode_tag_internal(ev_uint32_t *ptag, struct evbuffer *evbuf, int dodrain)
{...
 data = evbuffer_pullup(evbuf, len < sizeof(number) + 1 ? len : sizeof(number) + 1);
//evbuffer_pullup may return null.
//data is used below which causes dereferencing null
while (count++ < len) {
		ev_uint8_t lower = *data++;
//dereference: Incrementing a pointer which might be null: data might be null.
		number |= (lower & 0x7f) << shift;
		shift += 7;

		if (!(lower & 0x80)) {
			done = 1;
			break;
		}
	}
To resolve this checking data in while loop
line no 211 
while (count++ < len) { 
is replaced with 
while (count++ < len && data) {