Annotate non-empty-string

Author: sirreal

src/wp-includes/html-api/class-wp-html-tag-processor.php

@@ -2216,6 +2216,7 @@ private function parse_all_attributes(): void {
 			}
 
 			$attribute_start             = $this->bytes_already_parsed;
+			/** @phpstan-var non-empty-string $attribute_name */
 			$attribute_name              = substr( $this->html, $attribute_start, $name_length );
 			$this->bytes_already_parsed += $name_length;