fix(auth): return currentUser directly from the native instance (#69)

Author: canmertc

packages/firebase-auth/index.android.ts

@@ -1425,12 +1425,8 @@ export class Auth implements IAuth {
     return this.#app;
   }
 
-  #user: User;
   get currentUser(): User {
-    if (!this.#user) {
-      this.#user = User.fromNative(this.native.getCurrentUser());
-    }
-    return this.#user;
+    return this.native ? User.fromNative(this.native.getCurrentUser()) : null;
   }
 
   get languageCode(): string {

packages/firebase-auth/index.ios.ts

@@ -1247,12 +1247,8 @@ export class Auth implements IAuth {
 		return this.#app;
 	}
 
-	#user: User;
 	get currentUser(): User {
-		if (!this.#user) {
-			this.#user = User.fromNative(this.native.currentUser);
-		}
-		return this.#user;
+		return this.native ? User.fromNative(this.native.currentUser) : null;
 	}
 
 	get languageCode(): string {