Fix null handling in preg_replace calls inside normalize_content()

includes/helpers.php

@@ -42,19 +42,19 @@
 	 *
 	 * @return string The filtered Post content.
 	 */
 	$content = (string) apply_filters( 'ai_experiments_pre_normalize_content', $content );
 
 	// Strip HTML entities.
-	$content = preg_replace( '/&#?[a-z0-9]{2,8};/i', '', $content );
+	$content = preg_replace( '/&#?[a-z0-9]{2,8};/i', '', $content ) ?? $content;
 
 	// Replace HTML linebreaks with newlines.
-	$content = preg_replace( '#<br\s?/?>#', "\n\n", (string) $content );
+	$content = preg_replace( '#<br\s?/?>#', "\n\n", $content ) ?? $content;
 
 	// Strip all HTML tags.
 	$content = wp_strip_all_tags( (string) $content );
 
 	// Remove unrendered shortcode tags.
-	$content = preg_replace( '#\[.+\](.+)\[/.+\]#', '$1', $content );
+	$content = preg_replace( '#\[.+\](.+)\[/.+\]#', '$1', $content ) ?? $content;
 
 	/**
 	 * Filters the normalized content to allow for additional cleanup.
@@ -65,7 +65,7 @@
 	 *
 	 * @return string The filtered normalized content.
 	 */
 	$content = (string) apply_filters( 'ai_experiments_normalize_content', (string) $content );
 
 	return trim( $content );
 }
@@ -164,7 +164,7 @@
 	 * @param array<int, array{string, string}> $preferred_models The preferred models.
 	 * @return array<int, array{string, string}> The filtered preferred models.
 	 */
 	return (array) apply_filters( 'ai_experiments_preferred_models', $preferred_models );
 }
 
 /**
@@ -206,7 +206,7 @@
 	 * @param array<int, array{string, string}> $preferred_models The preferred image models.
 	 * @return array<int, array{string, string}> The filtered preferred image models.
 	 */
 	return (array) apply_filters( 'ai_experiments_preferred_image_models', $preferred_models );
 }
 
 /**
@@ -258,7 +258,7 @@
 	 * @param bool|null $has_valid_credentials Whether valid credentials are available. Return null to use default check.
 	 * @return bool|null True if valid credentials are available, false otherwise, or null to use default check.
 	 */
 	$valid = apply_filters( 'ai_experiments_pre_has_valid_credentials_check', null );
 	if ( null !== $valid ) {
 		return (bool) $valid;
 	}