Fix two bug in the TTS settings.

(a) The TTS API doesn't mandate that unavailable voices should
be set and null, so deal with it correctly.

(b) The android manifest contained a reference to the old
TTS class.

bug:5525023
Change-Id: I1c16dbc75893288e5fa221c73a7284fca7ab25c5
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 1da79f8..3326b5d 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -716,7 +716,7 @@
                 <category android:name="android.intent.category.DEFAULT" />
             </intent-filter>
             <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
-                android:value="com.android.settings.TextToSpeechSettings" />
+                android:value="com.android.settings.tts.TextToSpeechSettings" />
             <meta-data android:name="com.android.settings.TOP_LEVEL_HEADER_ID"
                 android:resource="@id/language_settings" />
         </activity>