--- mozilla-release-FIREFOX_70_0_RELEASE/media/ffvpx/libavcodec/utils.c.orig	2019-10-31 09:15:24.819410877 +0100
+++ mozilla-release-FIREFOX_70_0_RELEASE/media/ffvpx/libavcodec/utils.c	2019-10-31 09:13:52.736038110 +0100
@@ -421,7 +421,7 @@
             if (desc->comp[0].depth >= 9) {
                 for (x = 0; x<bytes; x++)
                     ((uint16_t*)dst)[x] = c[p];
-            }else
+            }else if (bytes>0)
                 memset(dst, c[p], bytes);
             dst += frame->linesize[p];
         }