avutil/tests/dict: Check av_dict_set() before get for failure

Failure is possible due to strdup()

Fixes: CID1516764 Dereference null return value

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit e8a1e1899d)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavutil/tests/dict.c

@@ -148,12 +148,15 @@ int main(void)
 
     //valgrind sensible test
     printf("\nTesting av_dict_set() with existing AVDictionaryEntry.key as key\n");
-    av_dict_set(&dict, "key", "old", 0);
+    if (av_dict_set(&dict, "key", "old", 0) < 0)
+        return 1;
     e = av_dict_get(dict, "key", NULL, 0);
-    av_dict_set(&dict, e->key, "new val OK", 0);
+    if (av_dict_set(&dict, e->key, "new val OK", 0) < 0)
+        return 1;
     e = av_dict_get(dict, "key", NULL, 0);
     printf("%s\n", e->value);
-    av_dict_set(&dict, e->key, e->value, 0);
+    if (av_dict_set(&dict, e->key, e->value, 0) < 0)
+        return 1;
     e = av_dict_get(dict, "key", NULL, 0);
     printf("%s\n", e->value);
     av_dict_free(&dict);