crash with empty password & username

[individual-it]

set HTTP username and password to an empty string and start hmb

export AUTH_USERNAME=
export AUTH_PASSWORD=
./hmb s --mqtt-host=tcp://10.4.1.1:1883

[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.

[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
 - using env:	export GIN_MODE=release
 - using code:	gin.SetMode(gin.ReleaseMode)

[GIN-debug] GET    /ping                     --> main.SetupGin.func1 (3 handlers)
[GIN-debug] GET    /                         --> main.SetupGin.func2 (3 handlers)
panic: User can not be empty

goroutine 1 [running]:
github.com/gin-gonic/gin.assert1(...)
	/home/pi/go/pkg/mod/github.com/gin-gonic/[email protected]/utils.go:79
github.com/gin-gonic/gin.processAccounts(0x2997adc, 0x5eaac9, 0xc, 0x2997a70)
	/home/pi/go/pkg/mod/github.com/gin-gonic/[email protected]/auth.go:75 +0x28c
github.com/gin-gonic/gin.BasicAuthForRealm(0x2997adc, 0x281e0c0, 0x24, 0x0)
	/home/pi/go/pkg/mod/github.com/gin-gonic/[email protected]/auth.go:48 +0xec
github.com/gin-gonic/gin.BasicAuth(...)
	/home/pi/go/pkg/mod/github.com/gin-gonic/[email protected]/auth.go:68
main.SetupGin(0x298aa40, 0x0)
	/home/pi/http-mqtt-bridge/main.go:158 +0x168
main.Setup(0x298aa40)
	/home/pi/http-mqtt-bridge/main.go:124 +0x28
main.main.func2(0x29d00b0, 0x0, 0x29d00b0)
	/home/pi/http-mqtt-bridge/main.go:91 +0x28
github.com/urfave/cli.HandleAction(0x555bf8, 0x60f298, 0x29d00b0, 0x2980400, 0x0)
	/home/pi/go/pkg/mod/github.com/urfave/[email protected]/app.go:490 +0x68
github.com/urfave/cli.Command.Run(0x5e5bbb, 0x5, 0x0, 0x0, 0x29841b0, 0x1, 0x1, 0x5ede0e, 0x11, 0x0, ...)
	/home/pi/go/pkg/mod/github.com/urfave/[email protected]/command.go:210 +0x780
github.com/urfave/cli.(*App).Run(0x29b00e0, 0x289a0e0, 0x3, 0x4, 0x0, 0x0)
	/home/pi/go/pkg/mod/github.com/urfave/[email protected]/app.go:255 +0x504
main.main()
	/home/pi/http-mqtt-bridge/main.go:97 +0x464