Protect against invalid authority in account sync pref.

Some apps might contain account synclets with empty authority. Settings
UI should protect against this type of synclets. Otherwise clicking on
these synclets will crash.

(Also removed some strings that are no longer needed)

Change-Id: I364b45fc67679aa287ff1e04e6f5ac749116543a
Fixes: 74240862
Test: robotests

src/com/android/settings/accounts/SyncStateSwitchPreference.java

@@ -21,6 +21,7 @@ import android.app.ActivityManager;
 import android.content.Context;
 import android.support.v14.preference.SwitchPreference;
 import android.support.v7.preference.PreferenceViewHolder;
+import android.text.TextUtils;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.View;
@@ -64,6 +65,7 @@ public class SyncStateSwitchPreference extends SwitchPreference {
         mAuthority = authority;
         mPackageName = packageName;
         mUid = uid;
+        setVisible(!TextUtils.isEmpty(mAuthority));
         notifyChanged();
     }