[UploadImage] Disable "Save" button when no image selected

[imnasnainaec]

Accessed in two different ways

• click avatar in top bar to open user menu > User Settings > click avatar in user settings to upload
• open a project > click gear in top bar to open project settings > Users > Manage speakers > add a speaker > click + to open consent menu options > Upload image consent

The dialog has a "Browse" and "Save" button. The save button doesn't do anything if Browse hasn't been used to select a file. The "Save" button should be disabled if no file is selected.