casbin 'enforce' api method throws exception

[typicalhuman7]

Seems casbin 'enforce' api method fail while serializes result to bool value. Casdoor response looks like an array with bool values [ "false" ]

https://github.com/casdoor/casdoor/blob/2fd2d88d20d470fedb72885c224cbae4e595f109/controllers/casbin_api.go#L71

[casbin-bot]

@seriouszyx @ComradeProgrammer @Resulte