Exception WebfingerHandler line 105

Hello,
I just want to ask if somebody also have this Error message:

Exception: strpos(): Argument #1 ($haystack) must be of type string, null given in file '/var/www/nextcloud/apps/social/lib/WellKnown/WebfingerHandler.php' line 105

I use a apache server with enabled social app 0.5.0beta3 and NC25.0.2

In the social app I don’t get message that webfinger is not set properly. But in ‘security & setup warning’ on administration page I get the warning that webfinger is not set properly.
And the above Exception is thrown when I use in browser:
https://myexample.com/.well-known/webfinger

When I use: https://myexample.com/.well-known/webfinger?resource=acct:michael@example.com
the JSON data is shown. Does anybody have an example how it must look like?
Here is my one:

subject	"michael@example.com"
aliases	
0	"https://example.com/nextcloud/index.php/apps/social@Michael"
1	"https://example.com/nextcloud/u/Michael"
links	
0	
rel	"self"
type	"application/activity+json"
href	"https://example.com/nextcloud/index.php/apps/social@Michael"
1	
rel	"http://webfinger.net/rel/profile-page"
type	"text/html"
href	"https://example.com/nextcloud/u/Michael"
2	
rel	"http://ostatus.org/schema/1.0/subscribe"
template	"https://example.com/nextcloud/apps/social/ostatus/follow/?uri={uri}"