Make hb-view err if all shapers failed

util/view-cairo.hh

diff --git a/util/view-cairo.hh b/util/view-cairo.hh
index 31c7ade..9b000b5 100644
--- a/util/view-cairo.hh
+++ b/util/view-cairo.hh
@@ -59,7 +59,7 @@
 		     unsigned int  text_len,
 		     hb_bool_t     utf8_clusters)
   {
-    consume_glyphs (buffer, text, text_len, utf8_clusters);
+    fail (false, "all shapers failed");
   }
   void consume_glyphs (hb_buffer_t  *buffer,
 		       const char   *text,