mxf_timestamp_to_str: dont leave uninitilaized fields in time.

Fixes CID1005318
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mxfdec.c

@@ -1660,7 +1660,7 @@ static int mxf_uid_to_str(UID uid, char **str)
 
 static int mxf_timestamp_to_str(uint64_t timestamp, char **str)
 {
-    struct tm time;
+    struct tm time = {0};
     time.tm_year = (timestamp >> 48) - 1900;
     time.tm_mon  = (timestamp >> 40 & 0xFF) - 1;
     time.tm_mday = (timestamp >> 32 & 0xFF);