patch 9.0.1143: invalid memory access with bad 'statusline' value

Problem:    Invalid memory access with bad 'statusline' value.
Solution:   Avoid going over the NUL at the end.

src/buffer.c

@@ -4617,6 +4617,8 @@ build_stl_str_hl(
 #endif
 	if (vim_strchr(STL_ALL, *s) == NULL)
 	{
+	    if (*s == NUL)  // can happen with "%0"
+		break;
 	    s++;
 	    continue;
 	}

src/testdir/test_statusline.vim

@@ -440,6 +440,13 @@ func Test_statusline()
   set splitbelow&
 endfunc
 
+func Test_statusline_trailing_percent_zero()
+  " this was causing illegal memory access
+  set laststatus=2 stl=%!%0
+  call assert_fails('redraw', 'E15: Invalid expression: "%0"')
+  set laststatus& stl&
+endfunc
+
 func Test_statusline_visual()
   func CallWordcount()
     call wordcount()

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1143,
 /**/
     1142,
 /**/