activated typescript strict mode

src/app/modules/songs/services/upload.ts

@@ -1,9 +1,8 @@
 export class Upload {
-  public $key: string;
   public file: File;
-  public name: string;
-  public path: string;
-  public progress: number;
+  public name = '';
+  public path = '';
+  public progress = 0;
   public createdAt: Date = new Date();
 
   public constructor(file: File) {