MT#55283 add missing (re-) initialiser

Change-Id: Iae96dc8018d646aadce8e7c229bcd7ee65b206bd
(cherry picked from commit 8e149723c0)

recording-daemon/mix.c

@@ -79,6 +79,7 @@ static void mix_input_reset(mix_t *mix, unsigned int idx) {
 	mix->pts_offs[idx] = (uint64_t) -1LL;
 	ZERO(mix->last_use[idx]);
 	mix->input_ref[idx] = NULL;
+	mix->in_pts[idx] = 0;
 }