Merge pull request #4362 from node-red/4342-subflow-err

Handle credential env var evaluation when no value set

packages/node_modules/@node-red/runtime/lib/flows/util.js

@@ -80,6 +80,7 @@ function mapEnvVarProperties(obj,prop,flow,config) {
 }
 
 async function evaluateEnvProperties(flow, env, credentials) {
+    credentials = credentials || {}
     const pendingEvaluations = []
     const evaluatedEnv = {}
     const envTypes = []