dynamic-stack-buffer-overflow in json_ptr::encode

[kcwu]

lnav version
master

To Reproduce
Steps to reproduce the behavior:

1. Build with ASAN.
2. printf '{"######################################0"0}\x0a' | ./lnav.asan -n

==4072977==ERROR: AddressSanitizer: dynamic-stack-buffer-overflow on address 0x7ffff31fb367 at pc 0x55555744de89 bp 0x7ffff31fb210 sp 0x7ffff31fb208                                                                             
WRITE of size 1 at 0x7ffff31fb367 thread T1                                                                                                                                                                                      
    #0 0x55555744de88 in json_ptr::encode(char*, unsigned long, char const*, unsigned long) /home/kcwu/fuzz/targets/lnav/lnav/src/yajlpp/json_ptr.cc:211:37                                                                      
    #1 0x55555744d8c4 in handle_map_key(void*, unsigned char const*, unsigned long) /home/kcwu/fuzz/targets/lnav/lnav/src/yajlpp/json_ptr.cc:124:20                                                                              
    #2 0x55555744a327 in yajl_do_parse /home/kcwu/fuzz/targets/lnav/lnav/src/yajl/yajl_parser.c:402:25                                                                                                                           
    #3 0x555557451950 in json_ptr_walk::parse(unsigned char const*, long) /home/kcwu/fuzz/targets/lnav/lnav/src/yajlpp/json_ptr.cc:564:19                                                                                        
    #4 0x555556548abd in json_ptr_walk::parse(string_fragment const&) /home/kcwu/fuzz/targets/lnav/lnav/src/./yajlpp/json_ptr.hh:66:22                                                                                           
    #5 0x555556548440 in json_ptr_walk::parse_fully(string_fragment const&) /home/kcwu/fuzz/targets/lnav/lnav/src/./yajlpp/json_ptr.hh:73:29                                                                                     
    #6 0x55555654428c in lnav::piper::multiplex_matcher::match(string_fragment const&) /home/kcwu/fuzz/targets/lnav/lnav/src/piper.match.cc:50:13                                                                                

found by afl++

[tstack]

Thanks for the report!