[CORE] fix to src/string.c:string_to_int(). If a NULL string is passed, the code would segfault on a null pointer dereference. Now, if a NULL string is passed, it returns 0. Not the prettiest fix ever.
[CORE] fix to src/string.c:string_to_int(). If a NULL string is passed, the code would segfault on a null pointer dereference. Now, if a NULL string is passed, it returns 0. Not the prettiest fix ever.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@30073 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot