assert fail in unquote

[kcwu]

lnav version
master

To Reproduce
Steps to reproduce the behavior:
echo H4sIAAAAAAAAA+NyNuBSMhgFo2AUGIAzAifx6jmxA7g8AMjRVHhdAwAA | base64 -d | gzip -d | lnav

#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at ./nptl/pthread_kill.c:44                                                                                             
#1  0x00007ffff749debf in __pthread_kill_internal (threadid=<optimized out>, signo=6) at ./nptl/pthread_kill.c:78                                                                                                                
#2  0x00007ffff7449d82 in __GI_raise (sig=6) at ../sysdeps/posix/raise.c:26                                                                                                                                                      
#3  0x000055555644ab3b in log_abort () at lnav_log.cc:644                                                                                                                                                                        
#4  0x000055555645709c in unquote (dst=dst@entry=0x5555582db690 "\273IN\rPU", str=<optimized out>, len=<optimized out>, len@entry=781) at string_util.cc:136                                                                     
#5  0x00005555562cd0ad in pretty_printer::write_element (this=this@entry=0x7fffffff93c0, el=...) at pretty_printer.cc:210                                                                                                        
#6  0x00005555562ce80b in pretty_printer::flush_values (this=this@entry=0x7fffffff93c0, start_on_depth=false) at pretty_printer.cc:279                                                                                           
#7  0x00005555562cbfd9 in pretty_printer::append_to (this=0x7fffffff93c0, al=...) at pretty_printer.cc:140                                                                                                                       
#8  0x0000555555f980f3 in textfile_sub_source::rescan_files (this=0x5555579c7938 <lnav_data+46512>, callback=..., deadline=std::optional [no contained value]) at textfile_sub_source.cc:1041                                    
#9  0x00005555557f02cd in rebuild_indexes (deadline=std::optional [no contained value]) at lnav.indexing.cc:243 
#10 0x00005555557f2ffa in rebuild_indexes_repeatedly () at lnav.indexing.cc:430                                                                                                                                                  
#11 0x000055555609943a in toggle_view (toggle_tc=toggle_tc@entry=0x5555579c2d20 <lnav_data+27032>) at view_helpers.cc:1190                                                                                                       
#12 0x00005555560a101d in ensure_view (expected_tc=0x5555579c2d20 <lnav_data+27032>) at view_helpers.cc:1231                                                                                                                     
#13 0x00005555557f039b in rebuild_indexes (deadline=std::optional [no contained value]) at lnav.indexing.cc:253 
#14 0x00005555557f2ffa in rebuild_indexes_repeatedly () at lnav.indexing.cc:430                                                                                                                                                  
#15 0x00005555556c7cd9 in main (argc=<optimized out>, argv=<optimized out>) at lnav.cc:3838                     

found by afl++

[tstack]

Thanks for the report