check this.compiler.outputFileSystem.constructor is not undefined

CHANGELOG.md

@@ -12,6 +12,10 @@ _Note: Gaps between patch versions are faulty, broken or test releases._
 
 ## UNRELEASED
 
+ * **Bug Fix**
+   * Fix failure with `compiler.outputFileSystem.constructor` being `undefined` ([#447](https://github.com/webpack-contrib/webpack-bundle-analyzer/pull/447) by [@kedarv](https://github.com/kedarv) and [@alexander-akait](https://github.com/alexander-akait))
+     * **NOTE:** This fix doesn't have added test coverage so the fix might break in future versions unless test coverage is added later.
+
 ## 4.4.1
 
  * **Bug Fix**

src/BundleAnalyzerPlugin.js

@@ -134,6 +134,9 @@ class BundleAnalyzerPlugin {
   }
 
   getBundleDirFromCompiler() {
+    if (typeof this.compiler.outputFileSystem.constructor === 'undefined') {
+      return this.compiler.outputPath;
+    }
     switch (this.compiler.outputFileSystem.constructor.name) {
       case 'MemoryFileSystem':
         return null;