avcodec/sanm: Fix uninitialized reference frames

Fixes: poc.snm

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit ca616b0f72)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/sanm.c

@@ -462,11 +462,11 @@ static void destroy_buffers(SANMVideoContext *ctx)
 
 static av_cold int init_buffers(SANMVideoContext *ctx)
 {
-    av_fast_padded_malloc(&ctx->frm0, &ctx->frm0_size, ctx->buf_size);
-    av_fast_padded_malloc(&ctx->frm1, &ctx->frm1_size, ctx->buf_size);
-    av_fast_padded_malloc(&ctx->frm2, &ctx->frm2_size, ctx->buf_size);
+    av_fast_padded_mallocz(&ctx->frm0, &ctx->frm0_size, ctx->buf_size);
+    av_fast_padded_mallocz(&ctx->frm1, &ctx->frm1_size, ctx->buf_size);
+    av_fast_padded_mallocz(&ctx->frm2, &ctx->frm2_size, ctx->buf_size);
     if (!ctx->version)
-        av_fast_padded_malloc(&ctx->stored_frame,
+        av_fast_padded_mallocz(&ctx->stored_frame,
                               &ctx->stored_frame_size, ctx->buf_size);
 
     if (!ctx->frm0 || !ctx->frm1 || !ctx->frm2 ||