Remove useless throws in boolbvt::convert_index

These invariant should already be ensured by the type.

Author: romainbrenguier

src/solvers/flattening/boolbv_index.cpp

@@ -17,12 +17,6 @@ Author: Daniel Kroening, [email protected]
 
 bvt boolbvt::convert_index(const index_exprt &expr)
 {
-  if(expr.id()!=ID_index)
-    throw "expected index expression";
-
-  if(expr.operands().size()!=2)
-    throw "index takes two operands";
-
   const exprt &array=expr.array();
   const exprt &index=expr.index();