non-focusable button, to avoid second interpretation of SPACE in C+e SPACE (isabelle.set-node-required);

--- a/src/Tools/jEdit/src/theories_dockable.scala	Sat Nov 30 15:05:10 2013 +0100
+++ b/src/Tools/jEdit/src/theories_dockable.scala	Sat Nov 30 16:07:00 2013 +0100
@@ -74,6 +74,7 @@
   }
 
   private val continuous_checking = new Isabelle.Continuous_Checking
+  continuous_checking.focusable = false
 
   private val logic = Isabelle_Logic.logic_selector(true)