Merge pull request #1013 from takkaw/fix_bo_missing

fix segmentation fault in BasicObject#inspect

src/class.c

@@ -1139,10 +1139,15 @@ mrb_bob_missing(mrb_state *mrb, mrb_value mod)
     mrb_raise(mrb, E_TYPE_ERROR, "name should be a symbol");
   }
 
+  if (mrb_respond_to(mrb,mod,mrb_intern(mrb,"inspect"))){
     inspect = mrb_funcall(mrb, mod, "inspect", 0);
     if (RSTRING_LEN(inspect) > 64) {
       inspect = mrb_any_to_s(mrb, mod);
     }
+  }
+  else {
+    inspect = mrb_any_to_s(mrb, mod);
+  }
 
   mrb_raisef(mrb, E_NOMETHOD_ERROR, "undefined method '%s' for %s",
       mrb_sym2name(mrb, mrb_symbol(name)), RSTRING_PTR(inspect));