fix: handle bad filePath from webpack (#114)

* handle uncaughtException

I do not know exactly what is the case in which this issue occurs, however this change should be enough to fix the issue.

Stacktrace:

```
uncaughtException TypeError: filePath.replace is not a function
    at WebpackPluginServe.socket.invalid (/project/node_modules/webpack-plugin-serve/lib/routes.js:80:35)
    at WebpackPluginServe.emit (events.js:194:15)
    at invalid.tap (/project/node_modules/webpack-plugin-serve/lib/index.js:155:41)
    at SyncHook.eval (eval at create (/project/node_modules/webpack/node_modules/tapable/lib/HookCodeFactory.js:19:10), <anonymous>:7:1)
    at Watchpack.watcher.compiler.watchFileSystem.watch (/project/node_modules/webpack/lib/Watching.js:139:33)
    at Object.onceWrapper (events.js:277:13)
    at Watchpack.emit (events.js:189:13)
    at Watchpack._onChange (/project/node_modules/watchpack/lib/watchpack.js:118:7)
    at Watchpack.<anonymous> (/project/node_modules/watchpack/lib/watchpack.js:109:8)
    at Watcher.emit (events.js:189:13)
    at /project/node_modules/watchpack/lib/DirectoryWatcher.js:101:9
    at Array.forEach (<anonymous>)
    at DirectoryWatcher.setFileTime (/project/node_modules/watchpack/lib/DirectoryWatcher.js:99:42)
    at DirectoryWatcher.onChange (/project/node_modules/watchpack/lib/DirectoryWatcher.js:264:7)
    at FSWatcher.emit (events.js:189:13)
    at FSWatcher.<anonymous> (/project/node_modules/watchpack/node_modules/chokidar/index.js:199:15)
    at /project/node_modules/watchpack/node_modules/chokidar/index.js:238:7
    at FSReqWrap.oncomplete (fs.js:155:5)
```

* pass down the filePath verbatim

Co-Authored-By: niieani <[email protected]>

Author: niieani

lib/routes.js

@@ -77,7 +77,7 @@ const setupRoutes = function setupRoutes() {
         }
 
         const context = compiler.context || compiler.options.context || process.cwd();
-        const fileName = filePath.replace(context, '');
+        const fileName = filePath.replace && filePath.replace(context, '') || filePath;
         const { wpsId } = compiler;
 
         socket.send(prep({ action: 'invalid', data: { fileName, wpsId } }));