Decrypt button disabled after dismissing password dialog

When decrypting a package, if one dismisses the password dialog, the decrypt button becomes disabled and cannot be re-enabled in any way.

Steps to reproduce:

1. Navigate to the decrypt page.
2. Select a package to decrypt.
3. Press decrypt.
4. Dismiss the password dialog - by pressing escape.

The decrypt button is now disabled 😠

Changing page re-enables it, but the password dialog doesn't show up anymore, leaving the app in a broken state. Could this be related to #258?