From cd7e46b62060bc03f61d42ddee12f6c4f08e1c67 Mon Sep 17 00:00:00 2001
From: Carsten Schmitz <carsten.schmitz@limesurvey.org>
Date: Tue, 17 Aug 2021 09:39:20 +0200
Subject: [PATCH] Fixed issue: Fatal error when using unary operator on empty
 string

---
 application/helpers/expressions/em_core_helper.php | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/application/helpers/expressions/em_core_helper.php b/application/helpers/expressions/em_core_helper.php
index 87359356645..7dee2191da2 100644
--- a/application/helpers/expressions/em_core_helper.php
+++ b/application/helpers/expressions/em_core_helper.php
@@ -554,6 +554,10 @@ private function RDP_EvaluateUnary(array $token)
             $this->RDP_AddError(self::gT("Invalid value(s) on the stack"), $token);
             return false;
         }
+        // If argmument is empty, then assume it is 0
+        if ($arg1[0] == '') {
+             $arg1[0] = 0;
+        };
         // TODO:  try to determine datatype?
         switch ($token[0]) {
             case '+':