remove const

datastream.c

@@ -103,6 +103,7 @@ static void render_frame(plm_t *mpeg, plm_frame_t *frame, void *d) {
 JSC_CCALL(os_make_video,
   size_t len;
   void *data = js_get_blob_data(js,&len,argv[0]);
+  if (data == -1) return JS_EXCEPTION;
   datastream *ds = ds_openvideo(data, len);
   if (!ds) return JS_ThrowReferenceError(js, "Video file was not valid.");
   ds->js = js;