VAAPI-XCB: check upper limit of cache_counter

It is possible for the cache_counter to reach its maximum value. In that case abort().

modules/codec/avcodec/vasub.c

@@ -22,6 +22,7 @@
 #endif
 
 #include <stdlib.h>
+#include <limits.h>
 #include <assert.h>
 
 #include <vlc_common.h>
@@ -71,6 +72,13 @@ static subpicture_cache_t *cache_new(void)
     if (cache == NULL)
         return NULL;
 
+    /* did we reach the maximum number of subpictures that can be created? */
+    if (cache_counter == UINT_MAX)
+    {
+        abort();
+        return NULL;
+    }
+
     cache->i_id = ++cache_counter;
     assert(cache_counter > 0);
     vlc_array_init(&cache->subpictures);