[Indic] Fix consonant position font lookup logic

Oops.  I broken this badly and the test suite did not notice.  That
worries me.  Have to investigate.

src/hb-ot-shape-complex-indic.cc

diff --git a/src/hb-ot-shape-complex-indic.cc b/src/hb-ot-shape-complex-indic.cc
index 7dde77d..ccc4a9d 100644
--- a/src/hb-ot-shape-complex-indic.cc
+++ b/src/hb-ot-shape-complex-indic.cc
@@ -340,9 +340,9 @@
 			      hb_codepoint_t *glyphs, unsigned int glyphs_len,
 			      hb_face_t      *face)
 {
-  if (indic_plan->pref.would_substitute (glyphs, ARRAY_LENGTH (glyphs), face)) return POS_BELOW_C;
-  if (indic_plan->blwf.would_substitute (glyphs, ARRAY_LENGTH (glyphs), face)) return POS_BELOW_C;
-  if (indic_plan->pstf.would_substitute (glyphs, ARRAY_LENGTH (glyphs), face)) return POS_POST_C;
+  if (indic_plan->pref.would_substitute (glyphs, glyphs_len, face)) return POS_BELOW_C;
+  if (indic_plan->blwf.would_substitute (glyphs, glyphs_len, face)) return POS_BELOW_C;
+  if (indic_plan->pstf.would_substitute (glyphs, glyphs_len, face)) return POS_POST_C;
   return POS_BASE_C;
 }