compile-directive throws java.lang.NullPointerException

[jimka2001]

An incomplete format directive at the end of the format string results in java.lang.NullPointerException.
There is code in cl_format.clj to handle this but the error handling is not reached because of the java exception.

To reproduce the error try any of the following

(cl-format true "~@")
(cl-format true "~:")
(cl-format true "~")

[jimka2001]

This issue is also discussed here
https://ask.clojure.org/index.php/10897/is-this-a-bug-in-cl-format?show=10900#c10900