asan report in _rl_isearch_dispatch

[Grisha Levit]

echo ':_' >/tmp/hist
HISTFILE=/tmp/hist ./bash --norc -in <<<$'\022:\023-\022'

==25246==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x0001039061d1 at pc 0x00010058faa4 bp 0x00016fdee0b0 sp
0x00016fdee0a8
READ of size 1 at 0x0001039061d1 thread T0

(lldb) fr s 5
frame #5: 0x000000010058faa4
bash`_rl_isearch_dispatch(cxt=0x0000000104202c50, c=18) at
isearch.c:776:14
   773 #endif
   774     }
   775   else
-> 776     found = STREQN (cxt->search_string, cxt->sline +
cxt->sline_index, cxt->search_string_index);
   777
   778   if (found)
   779     {

(lldb) fr v cxt->sline cxt->sline_index
(char *) cxt->sline = 0x00000001039061d0 ""
(int) cxt->sline_index = 1