[TECHNICAL SUPPORT] LPS-43311 Changing language causes "This URL can only be invoked using POST"

Hi Amos,

@peterborkuti sent me this PR to fix an issue when an error message is triggered and the user tries to change language then. I know it's pretty weird, but unfortunately it's still a valid use case based on our experience. 

I've reviewed the code and tested the fix, so it seems fine for me.

Please review it and push it forward if you find it OK. 

Should you have any concerns or questions, please let me know.

Vilmos