setup after download fails with {"message":"Invalid handler specified"}

[TMoersch]

I decided today to make an complete new installation from scratch on a different flush device
I could manage anything to work until I try now to install huawei_solar.
The download works, but not the setup??

Der Konfigurationsfluss konnte nicht geladen werden: {"message":"Invalid handler specified"}

Thanks

[wlcrs]

cfr. #264