Bug 63223 Use null to clear message text instead of empty string
I200405200800 StatusLine in jface uses setMessage("") to clear the text while the documentation says you should uset setMessage(null) to clear the text. The code path is slightly different for "" versus null, but using null makes the intent of the caller clearer.
bundles/org.eclipse.jface/src/org/eclipse/jface/action/StatusLine.java
data = DEFAULT_DATA;
                int width = w.computeSize(data.widthHint, h, flushCache).x;
                ws[i] = width;
                totalWidth += width + GAP;
            }
            int diff = rect.width - totalWidth;
            ws[0] += diff; 
            
            final int msgMinWidth = rect.width / 3;
            if (ws[0] < msgMinWidth) {
                diff = ws[0] - msgMinWidth;
                ws[0] = msgMinWidth;
            } else {
                diff = 0;
            }
            
            for (int i = count - 1; i >= 0 && diff < 0; --i) {
                int min = Math.min(ws[i], -diff);
                ws[i] -= min;
                diff += min + GAP;
            }
            int x = rect.x;
            int y = rect.y;
            for (int i = 0; i < count; i++) {
                Control w = children[i];
                /*
                 * Workaround for Linux Motif:
                 * Even if the progress bar and cancel button are
                 * not set to be visible ad of width 0, they still
                 * draw over the first pixel of the editor