check for lt returned by GetCachedInstance being null

Under some very weird circunstances that I haven't been able to reproduce but I'm seeing the logs for, lt is null. 
Since GetCachedInstance returns a null in some instances I would also argue this check should be in place anyways to avoid the null reference exception when the conditions for that null return occur.
Merge pull request #75 from raulvejar/patch-1

check for lt returned by GetCachedInstance being null
Proposed fix for #73. EarlyUrlLocalization redirection on unlocalized URLs now only happens with GET and HEAD methods. For other methods such as POST, redirection is avoided; instead the PrincipalApplicationLanguage for the request is inferred and the request handled without informing the browser (via the redirect) of the actual URL, not seen as an issue given that the URLs of POST methods etc. are not typically shown to the user.
Fix: postbuild exception when message.po file is absent for a locale language folder.
Improved support for default language: Added LocalizedApplication.MessageKeyIsValueInDefaultLanguage flag and removed requirement for PO file to exist in default language where the new MessageKeyIsValueInDefaultLanguage flag is set to true (the default). Also fixed bug in LanguageMatching algorithm which was preventing secondary grade matches being performed.
Updated readme to include Nugget section.
Readme fix
Readme updates for v2.0 release
Readme updates for v2.0 release
Readme tweaks
Readme tweaks
PostBuild: auto creation of locale folders and files
Merge pull request #85 from mdymel/v2.0

Thanks.
Readme tweaks
Readme tweaks
Readme tweaks
Catch exception in static cstor of LocalizedApplication (when called outside of http request handler context). Potential fix for issue #91.
Tweaked readme.
Fix for issue #92: PAL being incorrectly set to app's default language when EarlyUrlLocalization is disabled.

Optimization added to Matching algorithm.
Expanded default range of content-types translated to include text/plain and application/json. Ref issue #86 and #92.