Treafik 2.0 Fileupload not possible (Maybe Subfilter Issue?)

[DocEverdream]

Hello,

theres a problem with HTTP / SSL encryption with the Uploadform.

Via administration-panel it works perfect, but via Main-Page tehre a couple of Errors.

Firefox Console:
Laden von gemischten aktiven Inhalten "http://[SUB].[DOMAIN].com/ws.php?method=pwg.images.upload&format=json" wurde blockiert.
Uncaught SyntaxError: JSON.parse: unexpected end of data at line 1 column 1 of the JSON data

It seems equal to this Issue: #47
but i couldn't try the Fix, cause i don't know where in Traefik 2.0 i could configure subfilter directives.

Could anyone help me out?