add proper undefined checks

lib/src/http/response/FileResponseFactory.ts

@@ -38,6 +38,8 @@ export default class FileResponseFactory extends ResponseFactory {
         if ( content.headers && content.body && length ) {
             request.response.body = content.body
             request.response.headers.set('Content-Length', length)
+
+            if ( path.content_type )
                 request.response.headers.set('Content-Type', path.content_type)
         } else {
             this.logger.debug(`Tried to serve file that does not exist: ${path}`)

lib/src/support/UniversalPath.ts

@@ -102,6 +102,8 @@ export class UniversalPath {
     }
 
     get charset() {
+        if ( this.mime_type ) {
             return Mime.charset(this.mime_type)
         }
+    }
 }