patch 8.2.1037: Vim9: crash when using line continuation inside :def

Problem:    Vim9: crash when using line continuation inside :def.
Solution:   Check for no more lines available.

Author: brammool

src/testdir/test_vim9_func.vim

@@ -837,5 +837,16 @@ def Test_sort_return_type()
   res = [1, 2, 3]->sort()
 enddef
 
+def Line_continuation_in_def(dir: string = ''): string
+    let path: string = empty(dir)
+            \ ? 'empty'
+            \ : 'full'
+    return path
+enddef
+
+def Test_line_continuation_in_def()
+  assert_equal('full', Line_continuation_in_def('.'))
+enddef
+
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1037,
 /**/
     1036,
 /**/

src/vim9compile.c

@@ -2402,8 +2402,11 @@ peek_next_line(cctx_T *cctx)
     while (++lnum < cctx->ctx_ufunc->uf_lines.ga_len)
     {
 	char_u *line = ((char_u **)cctx->ctx_ufunc->uf_lines.ga_data)[lnum];
-	char_u *p = skipwhite(line);
+	char_u *p;
 
+	if (line == NULL)
+	    break;
+	p = skipwhite(line);
 	if (*p != NUL && !comment_start(p))
 	    return p;
     }