Fix checkboxgroup for unchecked submit

Author: vint47

src/Form/Element/CheckboxGroup.php

@@ -35,4 +35,9 @@ public function setOptions($options = [])
 
         return $this;
     }
+
+    public function value()
+    {
+        return $this->value ? : [];
+    }
 }

src/resources/views/default/element/checkbox-group.blade.php

@@ -1,6 +1,7 @@
 <div class="form__element form__element_type_checkbox-group @if($error) form__element_error @endif {{$class}}">
     <label class="form__label">{{ $label }}</label>
     <div class="form__element-container">
+        <input type="hidden" value="" name="{{ $elementName }}">
         @foreach ($options as $key => $label)
             <label>
                 <input @foreach($attributes as $attributeName => $attributeValue) {{ $attributeName }}="{{ $attributeValue }}" @endforeach type="checkbox"