Fix default field value (#69)

Co-authored-by: Yanick Witschi <[email protected]>

src/EventListener/LoadFormFieldListener.php

@@ -31,11 +31,15 @@ public function __invoke(Widget $widget, string $formId, array $formData, Form $
         // We only prefill the value if it was not submitted in this step.
         // If you submit a value in step 1, go to step 2, then go back to step 1 and submit a wrong value there, Contao
         // would display an error, but we'd prefill it again with the previous value which would make no sense.
-        // Moreover, we prefill with submitted data as priority (= validated submitted widget data) and otherwise fall
-        // back to potential previous post data which has not been validated yet (e.g. you filled in the values on step 2
-        // but then navigated back)
+        // We prefill in the following order:
+        // 1. Submitted data (= validated submitted widget data)
+        // 2. Fall back to potentially previously post data which has not been validated yet (e.g. you filled in the values
+        //    on step 2 but then navigated back)
+        // 3. The widget default value itself
         if (!$postData->has($widget->name)) {
-            $widget->value = $stepData->getSubmitted()->get($widget->name, $stepData->getOriginalPostData()->get($widget->name));
+            $widget->value = $stepData->getSubmitted()->get(
+                $widget->name, $stepData->getOriginalPostData()->get($widget->name, $widget->value)
+            );
         }
 
         return $widget;