ClearTypeFeedbackInfo(): context may not be initialized.

SharedFunctionInfo::ClearTypeFeedbackInfo() wants to compare feedback
to the array JSFunction, but it's called at times when the context
isn't fully initialized. Be cautious about this check.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/298983002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21434 ce2b1a6d-e550-0410-aec6-3dcde31c8c00