Incorrect highlighting of multiline descriptions

Created by: GeraldJansen

Multiline descriptions (with embedded newlines) are not properly handled in the overview window. As shown in the screenshots below, when selecting tasks with the up/down arrows, the first task gets highlighted with the size of the second task and vice-versa. The selection of tasks by clicking on them is also messed up because of incorrect height calculations. This may be related to #274 (closed) and #412. (For me this is low priority because I don't personally use descriptions, but I thought it worthwhile to document the issue anyway.)