Add stricter checks for the capabilities input

Author: pandah3

utils/class-capability-utils.php

@@ -83,7 +83,7 @@ public static function user_has_any_capability_full( $user, $capabilities ): boo
 
 		try {
 			foreach ( $capabilities as $capability ) {
-				if ( ! is_scalar( $capability ) ) {
+				if ( ! is_string( $capability ) || trim( $capability ) === '' ) {
 					continue;
 				}
 
@@ -129,7 +129,7 @@ public static function user_has_any_capability( $user, $capabilities ): bool {
 
 		foreach ( $capabilities as $capability ) {
 			// Skip non-scalar capabilities to prevent errors
-			if ( ! is_scalar( $capability ) ) {
+			if ( ! is_string( $capability ) || trim( $capability ) === '' ) {
 				continue;
 			}