proxy protocol-related memory leak at shutdown

$ ./mtr --debug-server --valgrind-mysqld read_only_persisted_plugin_variables
...
[100%] main.read_only_persisted_plugin_variables [ fail ]  Found warnings/errors in server log file!
...
==5826== 104 bytes in 1 blocks are possibly lost in loss record 1 of 1
==5826==    at 0x728367F: malloc (vg_replace_malloc.c:298)
==5826==    by 0x42130AA: my_raw_malloc(unsigned long, int) (my_malloc.cc:199)
==5826==    by 0x4212D02: my_malloc(unsigned int, unsigned long, int) (my_malloc.cc:81)
==5826==    by 0x4212E4B: my_realloc(unsigned int, void*, unsigned long, int) (my_malloc.cc:111)
==5826==    by 0x4AC6AF9: vio_proxy_protocol_add(st_vio_network const&) (viosocket.cc:684)
==5826==    by 0x2CD10EE: set_proxy() (mysqld.cc:2280)
==5826==    by 0x2CD2A17: network_init() (mysqld.cc:2643)
==5826==    by 0x2CDFE7A: mysqld_main(int, char**) (mysqld.cc:6611)
==5826==    by 0x2AFA2C9: main (main.cc:30)