fix: add a check for undefined environment values (#673)

* add a check for undefined environment values

Author: vtrifonov

Diff for: lib/compiler.js

@@ -135,6 +135,9 @@ function buildEnvCommandLineParams(config, envData, $logger) {
     const args = [];
     envFlagNames.map(item => {
         let envValue = envData[item];
+        if (typeof envValue === "undefined") {
+            return;
+        }
         if (typeof envValue === "boolean") {
             if (envValue) {
                 args.push(`--env.${item}`);