sanm: reset frame sizes on buffer destruction

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/sanm.c

@@ -231,6 +231,9 @@ static void destroy_buffers(SANMVideoContext *ctx)
     av_freep(&ctx->frm2);
     av_freep(&ctx->stored_frame);
     av_freep(&ctx->rle_buf);
+    ctx->frm0_size =
+    ctx->frm1_size =
+    ctx->frm2_size = 0;
 }
 
 static av_cold int init_buffers(SANMVideoContext *ctx)