module: remove unused code in module.js

Remove unnecessary condition in lib/module.js.

Refs: #18593 (comment)

PR-URL: #18768
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

lib/module.js

@@ -128,9 +128,6 @@ function readPackage(requestPath) {
     return false;
   }
 
-  if (json === '')
-    return packageMainCache[requestPath] = undefined;
-
   try {
     var pkg = packageMainCache[requestPath] = JSON.parse(json).main;
   } catch (e) {