This is the code fragment of the error:

(defn end-render
  [fb]
  (let [width (get-in fb [:dimen :width])
        height (get-in fb [:dimen :height])
        msfbo (:msfbo fb)
        fbo (:fbo fb)]
    (println fb)
    (GL33/glBindFramebuffer GL33/GL_READ_FRAMEBUFFER msfbo)
    (GL33/glBindFramebuffer GL33/GL_DRAW_FRAMEBUFFER fbo) ; this is line 116
    (GL33/glBlitFramebuffer 0 0 width height 0 0 width height GL33/GL_COLOR_BUFFER_BIT GL33/GL_NEAREST)
    (GL33/glBindFramebuffer GL33/GL_FRAMEBUFFER 0)))

from which I'm getting this error:

 = EXECUTION ERROR =
java.lang.NullPointerException: Cannot invoke "java.lang.Character.charValue()" because "x" is null
 - clojure.lang.RT: intCast (RT.java:1221)
 - breakout.fx$end_render: invokeStatic (fx.clj:116)
 - breakout.fx$end_render: invoke (fx.clj:108)
 - breakout.game$draw: invokeStatic (game.clj:245)
 - breakout.game$draw: invoke (game.clj:241)
 - util.window$game_loop: invokeStatic (window.clj:47)
 - util.window$game_loop: invoke (window.clj:37)
 - breakout.core$_main: invokeStatic (core.clj:14)

I've seen errors like this before, when I try to access an element in a map that isn't there. But that doesn't seem to be the case here. The output from the (println fb) looks fine:

{:dimen {:widht 800, :height 600}, :msfbo 1, :fbo 2, :rbo 1, :vao 2, :texture 7}

Note that the line number of the error might not be correct.

The full code can be found here.