Player: Remove option for country to be null.

model/src/main/java/changesets/operations/player/SetCurrentPlayerChangeset.java

@@ -62,14 +62,12 @@ public void applyInPlace(final @NotNull IMutableMap map) throws ChangesetFailure
 		final @NotNull String name1 = matchingOld.getName();
 		final @Nullable String country1 = matchingOld.country();
 		final @NotNull String portrait1 = matchingOld.portrait();
-		final Player matchingOldCopy = new PlayerImpl(playerId1, name1, Objects.requireNonNullElse(country1, ""), false,
-			portrait1);
+		final Player matchingOldCopy = new PlayerImpl(playerId1, name1, country1, false, portrait1);
 		final int playerId = matchingNew.playerId();
 		final @NotNull String name = matchingNew.getName();
 		final @Nullable String country = matchingNew.country();
 		final @NotNull String portrait = matchingNew.portrait();
-		final Player matchingNewCopy = new PlayerImpl(playerId, name, Objects.requireNonNullElse(country, ""), true,
-			portrait);
+		final Player matchingNewCopy = new PlayerImpl(playerId, name, country, true, portrait);
 		// TODO: try-catch here, in case the first operation fails?
 		map.replacePlayer(matchingOld, matchingOldCopy);
 		map.replacePlayer(matchingNew, matchingNewCopy);

model/src/main/java/common/map/Player.java

@@ -46,8 +46,8 @@ default String getPortrait() {
 	}
 
     /**
-     * The country the player is associated with. TODO: Should this be required to be unique in a map?
+     * The country the player is associated with. The empty string if not provided. TODO: Should this be required to be
+	 * unique in a map?
      */
-    @Nullable
     String country();
 }