object.c: fix up r51039

* object.c (convert_type): conversion without "to_" prefix is not
  implicit.  fix up r51039.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51115 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

object.c

@@ -2579,7 +2579,7 @@ static VALUE
 convert_type(VALUE val, const char *tname, const char *method, int raise)
 {
     ID m = 0;
-    int i;
+    int i = numberof(conv_method_names);
     VALUE r;
     static const char prefix[] = "to_";