Remove concept of 'unknown' recipient.

src/org/thoughtcrime/securesms/contacts/ContactSelectionListItem.java

@@ -73,7 +73,7 @@ public class ContactSelectionListItem extends LinearLayout implements RecipientF
 
     if (type == ContactRepository.NEW_TYPE) {
       this.recipient = null;
-      this.contactPhotoImage.setAvatar(glideRequests, Recipient.UNKNOWN, false);
+      this.contactPhotoImage.setAvatar(glideRequests, null, false);
     } else if (recipientId != null) {
       this.recipient = Recipient.live(recipientId);
       this.recipient.observeForever(this);

src/org/thoughtcrime/securesms/database/MmsDatabase.java

@@ -1542,7 +1542,7 @@ public class MmsDatabase extends MessagingDatabase {
       List<? extends Attachment> quoteAttachments = Stream.of(attachments).filter(Attachment::isQuote).toList();
       SlideDeck                  quoteDeck        = new SlideDeck(context, quoteAttachments);
 
-      if (quoteId > 0 && !quoteAuthor.isUnknown()) {
+      if (quoteId > 0) {
         return new Quote(quoteId, quoteAuthor, quoteText, quoteMissing, quoteDeck);
       } else {
         return null;

src/org/thoughtcrime/securesms/jobs/MmsDownloadJob.java

@@ -189,14 +189,12 @@ public class MmsDownloadJob extends BaseJob {
     String           body        = null;
     List<Attachment> attachments = new LinkedList<>();
 
-    RecipientId      from;
+    RecipientId from = null;
 
     if (retrieved.getFrom() != null) {
       from = Recipient.external(context, Util.toIsoString(retrieved.getFrom().getTextString())).getId();
     } else if (notificationFrom != null) {
       from = notificationFrom;
-    } else {
-      from = RecipientId.UNKNOWN;
     }
 
     if (retrieved.getTo() != null) {
@@ -211,7 +209,10 @@ public class MmsDownloadJob extends BaseJob {
       }
     }
 
-    members.add(from);
+    if (from != null) {
+      members.add(from);
+    }
+
     members.add(Recipient.self().getId());
 
     if (retrieved.getBody() != null) {

src/org/thoughtcrime/securesms/recipients/LiveRecipientCache.java

@@ -23,7 +23,6 @@ public final class LiveRecipientCache {
   private final Context                         context;
   private final RecipientDatabase               recipientDatabase;
   private final Map<RecipientId, LiveRecipient> recipients;
-  private final LiveRecipient                   unknown;
 
   private RecipientId localRecipientId;
 
@@ -32,13 +31,10 @@ public final class LiveRecipientCache {
     this.context           = context.getApplicationContext();
     this.recipientDatabase = DatabaseFactory.getRecipientDatabase(context);
     this.recipients        = new LRUCache<>(1000);
-    this.unknown           = new LiveRecipient(context, new MutableLiveData<>(), Recipient.UNKNOWN);
   }
 
   @AnyThread
   synchronized @NonNull LiveRecipient getLive(@NonNull RecipientId id) {
-    if (id.isUnknown()) return unknown;
-
     LiveRecipient live = recipients.get(id);
 
     if (live == null) {

src/org/thoughtcrime/securesms/recipients/Recipient.java

@@ -44,8 +44,6 @@ import java.util.Objects;
 
 public class Recipient {
 
-  public static final Recipient UNKNOWN = new Recipient(RecipientId.UNKNOWN);
-
   private final RecipientId            id;
   private final boolean                resolving;
   private final Address                address;

src/org/thoughtcrime/securesms/recipients/RecipientId.java

@@ -15,11 +15,8 @@ import java.util.List;
 
 public class RecipientId implements Parcelable, Comparable<RecipientId> {
 
-  private static final long UNKNOWN_ID = -1;
   private static final char DELIMITER = ',';
 
-  public static final RecipientId UNKNOWN = RecipientId.from(UNKNOWN_ID);
-
   private final long id;
 
   public static RecipientId from(long id) {
@@ -54,10 +51,6 @@ public class RecipientId implements Parcelable, Comparable<RecipientId> {
     return out;
   }
 
-  public boolean isUnknown() {
-    return id == UNKNOWN_ID;
-  }
-
   public @NonNull String serialize() {
     return String.valueOf(id);
   }