patch 9.0.0060: accessing uninitialized memory when completing long line

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

Author: brammool

src/insexpand.c

@@ -642,6 +642,7 @@ ins_compl_infercase_gettext(
 	    // growarray.  Add the character in the next round.
 	    if (ga_grow(&gap, IOSIZE) == FAIL)
 		return (char_u *)"[failed]";
+	    *p = NUL;
 	    STRCPY(gap.ga_data, IObuff);
 	    gap.ga_len = (int)STRLEN(IObuff);
 	}

src/testdir/test_ins_complete.vim

@@ -2108,6 +2108,13 @@ 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

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    60,
 /**/
     59,
 /**/