[indic] Fix infinite loop

Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=863044

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

@@ -789,7 +789,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan,
      * We could use buffer->sort() for this, if there was no special
      * reordering of pre-base stuff happening later...
      */
-    if (indic_plan->is_old_spec || end - base > 127)
+    if (indic_plan->is_old_spec || end - start > 127)
       buffer->merge_clusters (base, end);
     else
     {