No need to use an empty locale string for this.

src/main/java/com/gmail/nossr50/commands/party/PartyInfoCommand.java

@@ -97,6 +97,6 @@ public class PartyInfoCommand implements CommandExecutor {
 
         player.sendMessage(LocaleLoader.getString("Commands.Party.Members.Header"));
         player.sendMessage(LocaleLoader.getString("Commands.Party.MembersNear", membersNear, membersOnline));
-        player.sendMessage(LocaleLoader.getString("Commands.Party.Members", createMembersList()));
+        player.sendMessage(createMembersList());
     }
 }

src/main/resources/locale/locale_en_US.properties

@@ -464,7 +464,6 @@ Commands.Party.AlreadyExists=[[DARK_RED]]Party {0} already exists!
 Commands.Party.Kick=[[RED]]You were kicked from party {0}!
 Commands.Party.Leave=[[RED]]You have left that party
 Commands.Party.Members.Header=[[RED]]-----[][[GREEN]]MEMBERS[[RED]][]-----
-Commands.Party.Members={0}
 Commands.Party.None=[[RED]]You are not in a party.
 Commands.Party.Quit=[[RED]]- Leave your current party
 Commands.Party.Teleport=<player> [[RED]]- Teleport to party member