Modified predicate for activating checkers so that it can fallback to…

[didibus]

… using the major mode when there are no associated files with the Clojure buffer.

This allows flycheck-clj-kondo to be enabled and linting buffers that don't have a file associated with them. I often create buffers with no files and start a REPL just to mess and around, and I was missing having clj-kondo available in them.

I tested the following combination on my desktop:

• clojure-mode no file
• clojurec-mode no file
• clojurescript-mode no file
• clojure-mode with file
• clojurec-mode with file
• clojurescript-mode with file

[borkdude]

Thanks!