Correctly avoid displaying about category in groups

Fixes #7702

res/xml/recipient_preferences.xml

@@ -6,7 +6,7 @@
         <org.thoughtcrime.securesms.preferences.widgets.ContactPreference android:key="pref_key_number" android:persistent="false"/>
     </PreferenceCategory>
 
-    <PreferenceCategory android:layout="@layout/preference_divider"/>
+    <PreferenceCategory android:key="about_divider" android:layout="@layout/preference_divider"/>
 
     <PreferenceCategory android:key="notification_settings" android:title="@string/recipient_preferences__chat_settings">
         <org.thoughtcrime.securesms.components.SwitchPreferenceCompat
@@ -43,7 +43,7 @@
 
     <PreferenceCategory android:layout="@layout/preference_divider"/>
 
-    <PreferenceCategory android:title="@string/recipient_preferences__call_settings">
+    <PreferenceCategory android:key="call_settings" android:title="@string/recipient_preferences__call_settings">
 
         <org.thoughtcrime.securesms.preferences.widgets.SignalPreference
                 android:key="pref_key_recipient_call_ringtone"

src/org/thoughtcrime/securesms/RecipientPreferenceActivity.java

@@ -328,6 +328,7 @@ public class RecipientPreferenceActivity extends PassphraseRequiredActionBarActi
       Preference            blockPreference           = this.findPreference(PREFERENCE_BLOCK);
       Preference            identityPreference        = this.findPreference(PREFERENCE_IDENTITY);
       PreferenceCategory    aboutCategory             = (PreferenceCategory)this.findPreference("about");
+      PreferenceCategory    aboutDivider              = (PreferenceCategory)this.findPreference("about_divider");
       ContactPreference     aboutPreference           = (ContactPreference)this.findPreference(PREFERENCE_ABOUT);
       PreferenceCategory    privacyCategory           = (PreferenceCategory) this.findPreference("privacy_settings");
       PreferenceCategory    divider                   = (PreferenceCategory) this.findPreference("divider");
@@ -352,7 +353,8 @@ public class RecipientPreferenceActivity extends PassphraseRequiredActionBarActi
         if (identityPreference != null) identityPreference.setVisible(false);
         if (privacyCategory    != null) privacyCategory.setVisible(false);
         if (divider            != null) divider.setVisible(false);
-        if (aboutCategory      != null) aboutCategory.setVisible(false);
+        if (aboutCategory      != null) getPreferenceScreen().removePreference(aboutCategory);
+        if (aboutDivider       != null) getPreferenceScreen().removePreference(aboutDivider);
       } else {
         colorPreference.setColors(MaterialColors.CONVERSATION_PALETTE.asConversationColorArray(getActivity()));
         colorPreference.setColor(recipient.getColor().toActionBarColor(getActivity()));