Skip a cleanup if new_ole failed

On Appveyor, WIN32OLE sometimes fails due to a system shutdown, and
`@ie` is not assigned.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64815 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/ruby/library/win32ole/win32ole/ole_func_methods_spec.rb

@@ -9,7 +9,7 @@ platform_is :windows do
     end
 
     after :each do
-      @ie.Quit
+      @ie.Quit if @ie
     end
 
     it "raises ArgumentError if argument is given" do