Change class rendering.

Instead of relying on an attribute that is not always there,
check for the passed widget and decide which class to add.

hshassets/templatetags/bulma.py

 from django import template
 from django.utils.safestring import mark_safe
+from django.forms.widgets import TextInput, Textarea
 from hshassets.forms.utils import render_form_field, render_form_generics, render_form_errors
 from hshassets.forms.elements import Field
 
@@ -16,8 +17,10 @@ def bulma_form_fields(form):
         widget_classes = list()
 
         # not every form element in bulma has the 'input' css class, so we need to differ here
-        if getattr(field.field.widget, 'input_type', None) not in ['checkbox', 'radio']:
+        if isinstance(field.field.widget, TextInput):
             widget_classes.append("input")
+        elif isinstance(field.field.widget, Textarea):
+            widget_classes.append("textarea")
 
         # highlight fields with errors
         if field.errors: