Resource Bundle Editor: NullPointer exception when using (incorrect) capitalization of value sets

When using a capital in the value set name, lookup of the resource can throw a Nullpointer Exception.
To be verified: According to the Java Locale spec the language and country are case insensitive but the language always canonicalized to lower case and the country to uppercase.

Steps to reproduce:
1) Create a RBD and create a value set 'En' (Note the capital E)
2) Create a site jsp with <fmt:setLocale value="en_US"/> and use the resource bundle in that page
3) Load the page in the site
Expected: English translation is loaded. (or the default is shown if we don't want to support case insensitive names)
Actual:

[INFO] [talledLocalContainer] 13.07.2014 12:15:28 WARN http-bio-8080-exec-12 [SetHstBundleTag.getLocalizationContext:142] Failed to get bundle for basename: org.onehippo.hst.demo.resources.ProductResources. java.lang.NullPointerException