fix: 🥅 fix a plugin loading error

While reloading, plugin cache may not be deleted.
This happens when a loaded plugin encounters an error during reload.
This causes a deadlock in the unloading code.

So make sure cache is always deleted:
- ignore when an `unload()` function doesn't exist
- delete cache even if there are no `exports`

lib/index.js

@@ -47,7 +47,9 @@ function unloadplugin(pluginname, pluginpath) {
     const plugin = require.resolve(pluginpath)
     try {
         if (plugin && require.cache[plugin]) {
-            require.cache[plugin].exports.unload()
+            // `unload()` isn't exported sometimes,
+            // when plugin isn't properly loaded
+            require.cache[plugin].exports?.unload?.()
             delete plugins[pluginname]
             delete require.cache[plugin]
         }