CCM-11029: handle unset env var

Author: harrim91

infrastructure/terraform/components/sandbox/pre.sh

@@ -10,14 +10,13 @@ echo Running pre.sh
 echo "REGION=$REGION"
 echo "ENVIRONMENT=$ENVIRONMENT"
 echo "ACTION=$ACTION"
-echo "SKIP_SANDBOX_INSTALL=$SKIP_SANDBOX_INSTALL"
 
 
 if [ "${ACTION}" == "apply" ]; then
     cd $(git rev-parse --show-toplevel)
     echo "Building lambdas for distribution"
 
-    if [ -z "$SKIP_SANDBOX_INSTALL" ]; then
+    if [[ -z "${SKIP_SANDBOX_INSTALL:-}" ]]; then
       echo "Installing dependencies"
       make dependencies;
     else