[BUGFIX] Handle empty values with FormEngine radio fields

The bug report #102303 indicates that a TCA element type=radio
with items containing an empty string do not get properly
restored/persisted in FormEngine (Backend GUI input fields).

This is because empty attributes from HTML `<input>` fields are
not evaluated, and thus not restored and stored properly when
selected. `GeneralUtility::implodeAttributes()` calls do not
utilize the `keepBlankAttributes` parameter.

The report specifically mentions radio Element types, but also
effects checkboxes and `<option>` tags. An option tag without
a value submits the label of the option instead of an empty
value, so the attribute `value=""` is important.

The `CategoryElement` and `JsonElement` both already use
the parameter `keepBlankAttributes`, so the older FormEngine
Elements were probably not re-investigated.

See #102303 on details how to test this patch.

Docs [1] currently do not mention that "value" may not be
an empty string.

[1] https://docs.typo3.org/m/typo3/reference-tca/main/en-us/ColumnsConfig/Type/Radio/Properties/Items.html

Resolves: #102303
Releases: main, 12.4
Change-Id: Id6a978c391dfb3781e400361e18810a037fc12a6
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81823
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>

typo3/sysext/backend/Classes/Form/Element/RadioElement.php

@@ -103,7 +103,7 @@ public function render()
                 $radioElementAttrs['checked'] = 'checked';
             }
             $html[] = '<div class="form-check' . $disabled . '">';
-            $html[] =     '<input ' . GeneralUtility::implodeAttributes($radioElementAttrs, true) . $disabled . '>';
+            $html[] =     '<input ' . GeneralUtility::implodeAttributes($radioElementAttrs, true, true) . $disabled . '>';
             $html[] =     '<label class="form-check-label" for="' . $radioId . '">';
             $html[] =         htmlspecialchars($this->appendValueToLabelInDebugMode($label, $value));
             $html[] =     '</label>';

typo3/sysext/backend/Classes/Form/Element/SelectCheckBoxElement.php

@@ -204,7 +204,7 @@ public function render()
 
                     $tableRows[] = '<tr>';
                     $tableRows[] =    '<td class="col-checkbox">';
-                    $tableRows[] =        '<input ' . GeneralUtility::implodeAttributes($inputElementAttrs, true) . '>';
+                    $tableRows[] =        '<input ' . GeneralUtility::implodeAttributes($inputElementAttrs, true, true) . '>';
                     $tableRows[] =    '</td>';
                     $tableRows[] =    '<td class="col-title">';
                     $tableRows[] =        '<label class="label-block nowrap-disabled" for="' . $item['id'] . '">';

typo3/sysext/backend/Classes/Form/Element/SelectMultipleSideBySideElement.php

@@ -213,7 +213,7 @@ public function render()
 
             foreach ($selectableItemGroup['items'] as $item) {
                 $selectableItemsHtml[] = '
-                    <option ' . GeneralUtility::implodeAttributes($item['attributes'], true) . '>
+                    <option ' . GeneralUtility::implodeAttributes($item['attributes'], true, true) . '>
                         ' . htmlspecialchars($item['label']) . '
                     </option>';
             }

typo3/sysext/backend/Classes/Form/Element/SelectSingleBoxElement.php

@@ -212,7 +212,7 @@ protected function renderOptionElement($value, $label, array $attributes = [])
     {
         $attributes['value'] = $value;
         $html = [
-            '<option ' . GeneralUtility::implodeAttributes($attributes, true) . '>',
+            '<option ' . GeneralUtility::implodeAttributes($attributes, true, true) . '>',
                 htmlspecialchars($this->appendValueToLabelInDebugMode($label, $value), ENT_COMPAT, 'UTF-8', false),
             '</option>',