In version v2.12.0 the GraphiQL playground no longer works. I always get the error Cannot read property '1' of null in my response. In version v2.11.1 everything works fine.

Please tell us about your environment:
I can reproduce this issue. Looking into it now.
@grebsai As a quick workaround, give your query a name:
query MyQuery {
allNames {
id
title
}
}
I'll fix this shortly.
Most helpful comment
@grebsai As a quick workaround, give your query a name:
I'll fix this shortly.