Add error handling for buying with non-int productkey
Add error handling for buying with non-int productkey

oangervuori/namubufferi,mylvari/namubufferi,mylvari/namubufferi,mylvari/namubufferi,oangervuori/namubufferi,oangervuori/namubufferi,oangervuori/namubufferi,mylvari/namubufferi