Prevent a crash caused by empty emoji

The crash happens because the serialization of recently used emoji uses
';' to separate the emojis.
One of the ASCII emojis however has a ';' in the beginning.
When this one is used by the user,
it causes an empty string to be returned when deserializing.

This commit prevents the crash by changing the separator to a tab.
It uses a different settings string to store the emoji,
so users will lose the list of recently used emoji when they update to
this version.

PS. That wasn't my idea ;)

briar-android/src/main/java/org/thoughtcrime/securesms/components/emoji/EmojiPageView.java

@@ -104,8 +104,9 @@ public class EmojiPageView extends FrameLayout {
 								emojiSize + 2 * pad));
 				view = emojiView;
 			}
+			String emoji = model.getEmoji()[position];
+			view.setEmoji(emoji);
 
-			view.setEmoji(model.getEmoji()[position]);
 			return view;
 		}
 	}

briar-android/src/main/java/org/thoughtcrime/securesms/components/emoji/RecentEmojiPageModel.java

@@ -32,7 +32,7 @@ public class RecentEmojiPageModel implements EmojiPageModel {
 	private static final Logger LOG =
 			Logger.getLogger(RecentEmojiPageModel.class.getName());
 
-	private static final String EMOJI_LRU_PREFERENCE = "pref_emoji_recent";
+	private static final String EMOJI_LRU_PREFERENCE = "pref_emoji_recent2";
 	private static final int EMOJI_LRU_SIZE = 50;
 
 	private final LinkedHashSet<String> recentlyUsed; // UI thread
@@ -98,12 +98,12 @@ public class RecentEmojiPageModel implements EmojiPageModel {
 	}
 
 	private String serialize(LinkedHashSet<String> emojis) {
-		return StringUtils.join(emojis, ";");
+		return StringUtils.join(emojis, "\t");
 	}
 
 	private LinkedHashSet<String> deserialize(@Nullable String serialized) {
 		if (serialized == null) return new LinkedHashSet<>();
-		String[] list = serialized.split(";");
+		String[] list = serialized.split("\t");
 		LinkedHashSet<String> result = new LinkedHashSet<>(list.length);
 		Collections.addAll(result, list);
 		return result;