[ot] Don't mirror character if font doesn't support mirrored character!

src/hb-ot-shape.cc

diff --git a/src/hb-ot-shape.cc b/src/hb-ot-shape.cc
index a531d77..8d6bb3d 100644
--- a/src/hb-ot-shape.cc
+++ b/src/hb-ot-shape.cc
@@ -305,7 +305,7 @@
   hb_glyph_info_t *info = buffer->info;
   for (unsigned int i = 0; i < count; i++) {
     hb_codepoint_t codepoint = unicode->mirroring (info[i].codepoint);
-    if (likely (codepoint == info[i].codepoint))
+    if (likely (codepoint == info[i].codepoint || !c->font->has_glyph (codepoint)))
       info[i].mask |= rtlm_mask;
     else
       info[i].codepoint = codepoint;