fix null

Author: WillBeebe

CHANGELOG.md

@@ -4,6 +4,9 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.8.0] - 2021-02-18
+### Fixed
+- Null var
 ## [1.7.0] - 2021-02-18
 ### Changed
 - Bump devenv

variables.tf

@@ -20,11 +20,11 @@ variable "vscode_enabled" {
 }
 
 variable "workspace_image_tag" {
-  default = null
+  default = ""
   type    = string
 }
 
 variable "workspace_image_digest" {
-  default = null
+  default = ""
   type    = string
 }