Fix algo for br_if

Author: rossberg

document/core/appendix/algorithm.rst

@@ -213,8 +213,7 @@ Other instructions are checked in a similar manner.
        case (br_if n)
          error_if(ctrls.size() < n)
          pop_val(I32)
-         pop_vals(ctrls[n].label_types)
-         push_vals(ctrls[n].label_types)
+         push_vals(pop_vals(ctrls[n].label_types))
 
        case (br_table n* m)
          pop_val(I32)