Desktop: add vertical spacer at bottom of filter widget

This way we don't have this weird stretched out look.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

desktop-widgets/filterwidget2.ui

@@ -331,6 +331,19 @@
      </property>
     </widget>
    </item>
+   <item row="12" column="0">
+    <spacer name="verticalSpacer">
+     <property name="orientation">
+      <enum>Qt::Vertical</enum>
+     </property>
+     <property name="sizeHint" stdset="0">
+      <size>
+       <width>20</width>
+       <height>40</height>
+      </size>
+     </property>
+    </spacer>
+   </item>
   </layout>
  </widget>
  <customwidgets>