Fix code analysis

Author: naimsolong

phpstan.neon.dist

@@ -5,7 +5,6 @@ parameters:
     level: 5
     paths:
         - src
-        - database
     tmpDir: build/phpstan
     checkOctaneCompatibility: true
     checkModelProperties: true

src/Builder/CsvBuilder.php

@@ -29,8 +29,6 @@ public function build(): string
             $value = $this->data[$column] ?? '';
             if (is_array($value)) {
                 $csvRow[] = "'".json_encode($value, JSON_UNESCAPED_UNICODE)."'";
-            } elseif (is_null($value)) {
-                $csvRow[] = 'NULL';
             } elseif (is_numeric($value)) {
                 $csvRow[] = $value;
             } elseif (is_bool($value)) {