don't nuke focus on dialog open, fixes #1816

Closes #1816

Merge request studip/studip!1193

resources/assets/javascripts/bootstrap/forms.js

@@ -403,9 +403,7 @@ STUDIP.ready(function () {
     // and we trigger that namespaced event here, still all change handlers
     // will execute (which is bad due to $(select).change(form.submit())).
     $('select:not([multiple])').each(function() {
-        $(this)
-            .toggleClass('has-no-value', this.value === '')
-            .blur();
+        $(this).toggleClass('has-no-value', this.value === '');
     });
 });