fix default file reader bug

client/src/app/shared/helpers/tuple.ts

@@ -0,0 +1,15 @@
+export class Tuple<T, U> {
+  constructor(public first: T, public second: U) {}
+
+  public get(): [T, U] {
+    return [this.first, this.second];
+  }
+
+  public switchGet(elem: any): any{
+    if(elem == this.first){
+      return this.second;
+    } else {
+      return this.first;
+    }
+  }
+}