(js) Fix mail draft autosave in preferences

Fixes #3519

UI/Templates/PreferencesUI/UIxPreferences.wox

@@ -594,7 +594,8 @@
             <div layout="row" layout-align="start center">
               <p><var:string label:value="Auto save every"/></p>
               <md-input-container class="md-input-number" md-no-float="md-no-float">
-                <input type="number" min="0" label:aria-label="minutes" ng-model="preferences.defaults.SOGoMailAutoSave"/>
+                <input type="number" min="0" label:aria-label="minutes"
+                       ng-model="app.preferences.defaults.SOGoMailAutoSave"/>
               </md-input-container>
               <var:string label:value="minutes"/>
             </div>

UI/WebServerResources/js/Preferences/Preferences.service.js

@@ -23,6 +23,9 @@
 
       data.SOGoMailLabelsColors = labels;
 
+      // Mail editor autosave is a number of minutes or 0 if disabled
+      data.SOGoMailAutoSave = parseInt(data.SOGoMailAutoSave) || 0;
+
       // We convert our list of autoReplyEmailAddresses/forwardAddress into a string.
       // We also convert our date objects into real date, otherwise we'll have strings
       // or undefined values and the md-datepicker does NOT like this.