avfilter/vf_rotate: Check ff_draw_init2() return value

Fixes: NULL pointer dereference
Fixes: 3_343

Found-by: De3mond
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_rotate.c

@@ -288,7 +288,9 @@ static int config_props(AVFilterLink *outlink)
     double res;
     char *expr;
 
-    ff_draw_init2(&rot->draw, inlink->format, inlink->colorspace, inlink->color_range, 0);
+    ret = ff_draw_init2(&rot->draw, inlink->format, inlink->colorspace, inlink->color_range, 0);
+    if (ret < 0)
+        return ret;
     ff_draw_color(&rot->draw, &rot->color, rot->fillcolor);
 
     rot->hsub = pixdesc->log2_chroma_w;