Adding empty string as a value and making column search parameter opt…

…ional in request body (#323)

Co-authored-by: Dejan Jovic <[email protected]>

src/DataTableState.php

@@ -102,7 +102,7 @@ private function handleSearch(ParameterBag $parameters): void
     {
         foreach ($parameters->all()['columns'] ?? [] as $key => $search) {
             $column = $this->dataTable->getColumn((int) $key);
-            $value = $this->isInitial ? $search : $search['search']['value'];
+            $value = $this->isInitial ? $search : $search['search']['value'] ?? "";
 
             if ($column->isSearchable() && ('' !== trim($value))) {
                 $this->setColumnSearch($column, $value);