Added additional check before adding the ._error property (#1657)

* Update error.js

* fix: error.js formatting

Co-authored-by: Alex Sokolov <[email protected]>

Author: Alex-Sokolov

Diff for: packages/test-utils/src/error.js

@@ -5,7 +5,10 @@ function errorHandler(errorOrString, vm) {
   const error =
     typeof errorOrString === 'object' ? errorOrString : new Error(errorOrString)
 
-  vm._error = error
+  if (vm) {
+    vm._error = error
+  }
+
   throw error
 }