Fix: Handle null content_type in hasErrorClickhouse()

[nzsakib]

Issue

We were flooded with lot of TypeError when we upgraded to smi2/phpClickHouse version 1.6.0
This is the error we found in our log:

TypeError
ClickHouseDB\Statement::hasErrorClickhouse(): Argument #2 ($contentType) must be of type string, null given, called in /home/www/client_api/vendor/smi2/phpclickhouse/src/Statement.php on line 226

This null case should be handled properly as $this->response()->content_type() Curl can return null on content type

Summary

• Fixes a potential fatal error when content_type is null in the hasErrorClickhouse() method
• Changes the $contentType parameter type from string to ?string to accept null values
• Adds explicit null check before calling stripos() to prevent type errors

Changes

• Modified Statement.php:155 to accept nullable content type parameter
• Added null safety check in conditional logic