Common realloc mistake: 'file_append' nulled but not freed upon failure

Link: https://lkml.kernel.org/r/20230426010527.703093-1-zenghao@kylinos.cnSigned-off-by: Hao Zeng <zenghao@kylinos.cn>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>