Fix segfault with Arabic combining marks
diff --git a/src/hb-ot-shape-complex-arabic.cc b/src/hb-ot-shape-complex-arabic.cc
index 4055e36..584fc51 100644
--- a/src/hb-ot-shape-complex-arabic.cc
+++ b/src/hb-ot-shape-complex-arabic.cc
@@ -689,8 +689,10 @@
 
     unsigned int this_type = get_joining_type (c->buffer->info[i].codepoint, c->buffer->unicode->v.get_general_category (c->buffer->info[i].codepoint));
 
-    if (unlikely (this_type == JOINING_TYPE_T))
+    if (unlikely (this_type == JOINING_TYPE_T)) {
+      c->buffer->info[i].gproperty = NONE;
       continue;
+    }
 
     const arabic_state_table_entry *entry = &arabic_state_table[state][this_type];