buglist bug 7257: normalize(subst(asin(z),z=-1)) division by zero

(1) -> normalize(subst(asin(z),z=-1))

   >> Error detected within library code:
   catdef: division by zero

(1) -> asin(-1)

          %pi
   (1)  - ---
           2
                                                    Type: Expression(Integer)
(2) -> subst(asin(z),z=-1)

   (2)  asin(- 1)
                                                    Type: Expression(Integer)
(3) -> normalize %

   >> Error detected within library code:
   catdef: division by zero

(3) -> normalize %%(1)

          %pi
   (3)  - ---
           2
                                                    Type: Expression(Integer)
(4) -> normalize(asin(- 1))

          %pi
   (4)  - ---
           2
                                                    Type: Expression(Integer)