added midnight to settings.ui

src/settings.ui

@@ -26,7 +26,7 @@
    <item>
     <widget class="QTabWidget" name="tabWidget">
      <property name="currentIndex">
-      <number>3</number>
+      <number>1</number>
      </property>
      <widget class="QWidget" name="tab">
       <attribute name="title">
@@ -430,6 +430,11 @@
            <string>dark</string>
           </property>
          </item>
+         <item>
+          <property name="text">
+           <string>midnight</string>
+          </property>
+         </item>
         </widget>
        </item>
        <item row="14" column="0" colspan="2">