Make sure no player already has the reserved UID when creating and account.

src/main/java/emu/grasscutter/database/DatabaseHelper.java

@@ -38,10 +38,18 @@ public final class DatabaseHelper {
 			if (reservedId == GameConstants.SERVER_CONSOLE_UID) {
 				return null;
 			}
+
+			// Make sure not other accounts has that id as its reservedPlayerId
 			exists = DatabaseHelper.getAccountByPlayerId(reservedId);
 			if (exists != null) {
 				return null;
 			}
+
+			// Make sure no existing player already has this id.
+			Player existsPlayer = DatabaseHelper.getPlayerByUid(reservedId);
+			if (existsPlayer != null) {
+				return null;
+			}
 		}
 
 		// Account

src/main/resources/languages/en-US.json

@@ -103,7 +103,7 @@
     "account": {
       "modify": "Modify user accounts",
       "invalid": "Invalid UID.",
-      "exists": "Account already exists.",
+      "exists": "An account with this username and/or UID already exists.",
       "create": "Account created with UID %s.",
       "delete": "Account deleted.",
       "no_account": "Account not found.",