prevent duplicate account creation

stickup.py

@@ -41,6 +41,12 @@ async def index(request):
 		if form_type == 'change_password':
 			result = await forms.change_password(request, user_data)
 		elif form_type == 'new_email':
+			if user_data:
+				result = {
+					'ok': False,
+					'message': "You already have an email account."
+				}
+				return render_template('index.html', request, locals())
 			result = await forms.new_email(request)
 			if result['ok']:
 				email = request['meta']['username'] + '@' +config.server_domain