Make sure we print something when user does not exist

Kind of a corner case, but if the user being added to the selection list
no longer exists, then the ID is added but the name is printed as an
empty string, resulting in incorrect behavior (the first empty string is
selected, so when record is saved the field is set to blank).

Follow-up fix for issue #19574

core/print_api.php

@@ -303,7 +303,17 @@ function print_user_option_list( $p_user_id, $p_project_id = null, $p_access = A
 		$p_user_id != NO_USER &&
 		!array_key_exists( $p_user_id, $t_users )
 	) {
-		$t_users[$p_user_id] = user_get_row( $p_user_id );
+		$t_row = user_get_row( $p_user_id );
+		if( $t_row === false ) {
+			# User doesn't exist - create a dummy record for display purposes
+			$t_name = user_get_name( $p_user_id );
+			$t_row = array(
+				'id' => $p_user_id,
+				'username' => $t_name,
+				'realname' => $t_name,
+			);
+		}
+		$t_users[$p_user_id] = $t_row;
 	}
 
 	$t_display = array();