Hide link device preference if we're a secondary device.

src/org/thoughtcrime/securesms/ApplicationPreferencesActivity.java

@@ -180,8 +180,12 @@ public class ApplicationPreferencesActivity extends PassphraseRequiredActionBarA
         .setOnPreferenceClickListener(new CategoryClickListener(PREFERENCE_CATEGORY_PUBLIC_KEY));
       this.findPreference(PREFERENCE_CATEGORY_QR_CODE)
         .setOnPreferenceClickListener(new CategoryClickListener(PREFERENCE_CATEGORY_QR_CODE));
-      this.findPreference(PREFERENCE_CATEGORY_LINK_DEVICE)
-        .setOnPreferenceClickListener(new CategoryClickListener(PREFERENCE_CATEGORY_LINK_DEVICE));
+
+      Preference linkDevicePreference = this.findPreference(PREFERENCE_CATEGORY_LINK_DEVICE);
+      // Hide if we're already a secondary device
+      linkDevicePreference.setVisible(!TextSecurePreferences.isSecondaryDevice(getContext()));
+      linkDevicePreference.setOnPreferenceClickListener(new CategoryClickListener(PREFERENCE_CATEGORY_LINK_DEVICE));
+
       this.findPreference(PREFERENCE_CATEGORY_SEED)
         .setOnPreferenceClickListener(new CategoryClickListener((PREFERENCE_CATEGORY_SEED)));