clarified indentation;

--- a/src/Tools/jEdit/src/completion_popup.scala	Sat Jun 24 11:02:32 2017 +0200
+++ b/src/Tools/jEdit/src/completion_popup.scala	Sat Jun 24 11:14:23 2017 +0200
@@ -367,7 +367,9 @@
           }
         }
 
-        if (!special) Isabelle.indent_input(text_area)
+        val selection = text_area.getSelection()
+        if (!special && (selection == null || selection.length == 0))
+          Isabelle.indent_input(text_area)
       }
     }