From 31af36b8bde129924053049038b8b3dd0d6cc6e9 Mon Sep 17 00:00:00 2001
From: Romain Dunand <romain@1-more-thing.com>
Date: Sun, 1 Dec 2019 23:08:37 +0100
Subject: [PATCH] Fix #139

Prevent null values from beeing treaded as objects
---
 packages/workflow/src/Workflow.ts | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/packages/workflow/src/Workflow.ts b/packages/workflow/src/Workflow.ts
index 9efaaa67ec..b48e380edf 100644
--- a/packages/workflow/src/Workflow.ts
+++ b/packages/workflow/src/Workflow.ts
@@ -865,16 +865,16 @@ export class Workflow {
 		// Execute the expression
 		try {
 			const returnValue = tmpl.tmpl(parameterValue, dataProxy.getDataProxy());
-			if (typeof returnValue === 'object' && Object.keys(returnValue).length === 0) {
-				// When expression is incomplete it returns a Proxy which causes problems.
-				// Catch it with this code and return a proper error.
-				throw new Error('Expression is not valid.');
+			if (returnValue !== null && typeof returnValue === 'object') {
+				if (Object.keys(returnValue).length === 0) {
+					// When expression is incomplete it returns a Proxy which causes problems.
+					// Catch it with this code and return a proper error.
+					throw new Error('Expression is not valid.');
+				}
+				if (returnObjectAsString === true)  {
+					return this.convertObjectValueToString(returnValue);
+				}
 			}
-
-			if (returnObjectAsString === true && typeof returnValue === 'object') {
-				return this.convertObjectValueToString(returnValue);
-			}
-
 			return returnValue;
 		} catch (e) {
 			throw new Error('Expression is not valid.');