Document_View.text_area_extension: do not insist in crashing if (weak) assertion is violated;

--- a/src/Tools/jEdit/src/jedit/document_view.scala	Sun Aug 29 22:47:36 2010 +0200
+++ b/src/Tools/jEdit/src/jedit/document_view.scala	Mon Aug 30 10:36:55 2010 +0200
@@ -175,7 +175,7 @@
                   text_area.offsetToXY(line_start max snapshot.convert(command_start))
                 val q =
                   text_area.offsetToXY(line_end min snapshot.convert(command_start + command.length))
-                assert(p.y == q.y)
+                if (p.y != q.y) System.err.println("Unexpected coordinates: " + p + ", " + q)
                 gfx.setColor(Document_View.choose_color(snapshot, command))
                 gfx.fillRect(p.x, y, q.x - p.x, line_height)
               }