avformat/mov: Use 64bit for str_size

We assign a 64bit variable to it before checking

Fixes: CID1604544 Overflowed integer argument

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 046d069552)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -303,7 +303,8 @@ static int mov_read_udta_string(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     char *str = NULL;
     const char *key = NULL;
     uint16_t langcode = 0;
-    uint32_t data_type = 0, str_size, str_size_alloc;
+    uint32_t data_type = 0, str_size_alloc;
+    uint64_t str_size;
     int (*parse)(MOVContext*, AVIOContext*, unsigned, const char*) = NULL;
     int raw = 0;
     int num = 0;