PHP warning from ob_clean() when no output buffer is active

Problem/Motivation

In production environments, the Tablefield module triggers a PHP warning when calling ob_clean() while no output buffer is active.

Steps to reproduce

This issue does not reproduce locally, likely due to differences in PHP configuration (e.g. output_buffering, zlib.output_compression) or execution order. When the output buffer may already be closed when Tablefield executes ob_clean(), resulting in the following warning:

ob_clean(): failed to delete buffer. No buffer to delete

This can cause noisy logs or, depending on error handling, break the request.

Proposed resolution

Wrap the ob_clean() call with a defensive check to ensure an active output buffer exists before attempting to clean it. For example:

if (ob_get_level() > 0) {
  ob_clean();
}