The setAD_User_ID (0) ensures persistence of the record to be System

and
avoid a new record. This idea was borrowed from remarks in X_AD_User.

Tested fully with various logins and changes to few records including
SuperUser and System. Hit a mandatory exception which is not fatal.

base/src/org/compiere/model/MUser.java

@@ -269,6 +269,7 @@ public class MUser extends X_AD_User
 		super (ctx, AD_User_ID, trxName);	//	0 is also System
 		if (AD_User_ID == 0)
 		{
+			setAD_User_ID (0); //red1 [ 1722226 ] Password for user System can't be changed 
 			setIsFullBPAccess (true);
 			setNotificationType(NOTIFICATIONTYPE_EMail);
 		}