Take document trimming into account with new line indicator.

Fixes CLIENT-272

Change-Id: I7fadc16777bfd6f5a5de180d4a747e03aaf1a841
Reviewed-on: http://gerrit.dmdirc.com/2076
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>

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

             /** {@inheritDoc}. */
             @Override
             public void run() {
+                lastSeenLine -= numTrimmed;
                 final LinePosition selectedRange = getSelectedRange();
                 selectedRange.setStartLine(selectedRange.getStartLine()
                         - numTrimmed);