Settings crashes on opening Wi-Fi Add network

Since Theme_Settings_NoActionBar extends from Theme.DeviceDefault.Settings,
so it carshed when AppCompatDelegateImpl tried to get AppCompat theme from WifiDialog.

Test: visual inspection, robo
Change-Id: I751b771fdfa9ad2261baa5a06274f6bb0a70d677
Fixes: 111804691

tests/robotests/src/com/android/settings/wifi/WifiDialogTest.java

@@ -37,7 +37,7 @@ public class WifiDialogTest {
         WifiDialog fullscreen = WifiDialog.createFullscreen(mContext, mListener, mockAccessPoint,
                 WifiConfigUiBase.MODE_CONNECT);
         assertThat(fullscreen.getContext().getThemeResId())
-                .isEqualTo(R.style.Theme_Settings_NoActionBar);
+                .isEqualTo(R.style.Theme_Settings_WifiDialogFullScreen);
     }
 
     @Test