redis-check-aof.c: Avoid leaking file handle if file is zero bytes (#12797)

If fopen() is successful, but redis_fstat() determines the file is zero
bytes, the file handle stored in fp will leak. This change closes the
filehandle stored in fp if the file is zero bytes.

An FD leak on a tool like redis-check-aof isn't an issue (it'll exit soon anyway).
This is just a cleanup.

src/redis-check-aof.c

@@ -238,6 +238,7 @@ int checkSingleAof(char *aof_filename, char *aof_filepath, int last_file, int fi
 
     off_t size = sb.st_size;
     if (size == 0) {
+        fclose(fp);
         return AOF_CHECK_EMPTY;
     }