Fixes textpane not autoscrolling on creation.

Change-Id: If3499a631e9dfe919bb1dab480c7c01504e39dc0
Reviewed-on: http://gerrit.dmdirc.com/1168
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Chris Smith <chris@dmdirc.com>

src/com/dmdirc/addons/ui_swing/textpane/TextPane.java

@@ -115,6 +115,8 @@ public final class TextPane extends JComponent implements MouseWheelListener,
             }
         };
         addMouseMotionListener(doScrollRectToVisible);
+
+        setScrollBarMax(document.getNumLines(), document.getNumLines());
     }
 
     /** {@inheritDoc} */