Fix yaml_document_delete

Remove unneeded context, which is not set in any macro.

src/api.c

@@ -1117,8 +1117,5 @@
 YAML_DECLARE(void)
 yaml_document_delete(yaml_document_t *document)
 {
-    struct {
-        yaml_error_type_t error;
-    } context;
     yaml_tag_directive_t *tag_directive;
 
@@ -1123,7 +1120,5 @@
     yaml_tag_directive_t *tag_directive;
 
-    context.error = YAML_NO_ERROR;  /* Eliminate a compliler warning. */
-
     assert(document);   /* Non-NULL document object is expected. */
 
     while (!STACK_EMPTY(&context, document->nodes)) {