[Indic] Handle overstruck matra position

src/hb-ot-shape-complex-indic-private.hh

@@ -139,8 +139,8 @@ enum indic_matra_category_t {
   INDIC_MATRA_CATEGORY_TOP_AND_RIGHT		= INDIC_MATRA_CATEGORY_RIGHT,
 
   INDIC_MATRA_CATEGORY_INVISIBLE		= INDIC_MATRA_CATEGORY_NOT_APPLICABLE,
-  INDIC_MATRA_CATEGORY_OVERSTRUCK		= INDIC_MATRA_CATEGORY_NOT_APPLICABLE,
-  INDIC_MATRA_CATEGORY_VISUAL_ORDER_LEFT	= INDIC_MATRA_CATEGORY_NOT_APPLICABLE
+  INDIC_MATRA_CATEGORY_OVERSTRUCK		= POS_AFTER_MAIN,
+  INDIC_MATRA_CATEGORY_VISUAL_ORDER_LEFT	= POS_PRE_M
 };
 
 /* Note: We use ASSERT_STATIC_EXPR_ZERO() instead of ASSERT_STATIC_EXPR() and the comma operation
@@ -222,7 +222,7 @@ matra_position (hb_codepoint_t u, indic_position_t side)
     case POS_ABOVE_C:	return MATRA_POS_TOP (u);
     case POS_BELOW_C:	return MATRA_POS_BOTTOM (u);
   };
-  abort ();
+  return side;
 }