d3d11va: check for malloc failure

libavcodec/d3d11va.c

@@ -20,7 +20,10 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include <stddef.h>
+
 #include "config.h"
+#include "libavutil/error.h"
 #include "libavutil/mem.h"
 
 #include "d3d11va.h"
@@ -28,6 +31,8 @@
 AVD3D11VAContext *av_d3d11va_alloc_context(void)
 {
     AVD3D11VAContext* res = av_mallocz(sizeof(AVD3D11VAContext));
+    if (!res)
+        return NULL;
     res->context_mutex = INVALID_HANDLE_VALUE;
     return res;
 }