vim-patch:9.0.0060: accessing uninitialized memory when completing long line

Problem:    Accessing uninitialized memory when completing long line.
Solution:   Terminate string with NUL.
b9e717367c

src/nvim/insexpand.c

@@ -582,6 +582,7 @@ static char_u *ins_compl_infercase_gettext(char_u *str, int char_len, int compl_
       // getting to six bytes from the edge of IObuff switch to using a
       // growarray.  Add the character in the next round.
       ga_grow(&gap, IOSIZE);
+      *p = NUL;
       STRCPY(gap.ga_data, IObuff);
       gap.ga_len = (int)STRLEN(IObuff);
     } else {

src/nvim/testdir/test_ins_complete.vim

@@ -965,6 +965,13 @@ func Test_infercase_very_long_line()
   exe "normal 2Go\<C-X>\<C-L>\<Esc>"
   call assert_equal(longLine, getline(3))
 
+  " check that the too long text is NUL terminated
+  %del
+  norm o
+  norm 1987ax
+  exec "norm ox\<C-X>\<C-L>"
+  call assert_equal(repeat('x', 1987), getline(3))
+
   bwipe!
   set noic noinfercase
 endfunc