fix possible null value of public key

app/lib/encryption/encryption.ts

@@ -203,6 +203,10 @@ class Encryption {
 		// This public key is already encoded using EJSON.stringify in the `persistKeys` method
 		const publicKey = UserPreferences.getString(`${server}-${E2E_PUBLIC_KEY}`);
 
+		if (!publicKey) {
+			throw new Error('Public key not found in local storage, password not changed');
+		}
+
 		// Send the new keys to the server
 		await Services.e2eSetUserPublicAndPrivateKeys(publicKey, encodedPrivateKey);
 	};