Site gives server error (NullPointerException) when resource bundle document contains keys with invalid language

Scenario, testsuite with resource bundle editor
1) In the
org.onehippo.hst.demo.resources.ProductResources
RBD add a key set with the name 'xxx'. Save the document
2) Load the site
Expected: site loads
Actual: 500 server error. java.lang.NullPointerException logged

Scenario: case sensitvity
1) In the
org.onehippo.hst.demo.resources.ProductResources
RBD rename the key set with the name 'en' to 'En'. Save the document.
Expected: site loads
Actual: 500 server error. java.lang.NullPointerException logged

Note that the RBD editor is case sensitive and allows keyset names with the same letters but different case. For example en and En. To be verified if we must allow this in the RBD editor