patch 8.2.0237: crash when setting 'wincolor' on finished terminal window

Problem:    Crash when setting 'wincolor' on finished terminal window.
            (Bakudankun)
Solution:   Check that the vterm is not NULL. (Yasuhiro Matsumoto, closes
            #5607, closes #5610)

Author: brammool

src/terminal.c

@@ -4276,6 +4276,8 @@ term_update_colors(void)
 {
     term_T *term = curwin->w_buffer->b_term;
 
+    if (term->tl_vterm == NULL)
+	return;
     init_default_colors(term, curwin);
     vterm_state_set_default_colors(
 	    vterm_obtain_state(term->tl_vterm),

src/testdir/test_terminal.vim

@@ -2370,3 +2370,18 @@ func Test_terminal_in_popup()
   call StopVimInTerminal(buf)
   call delete('XtermPopup')
 endfunc
+
+func Test_issue_5607()
+  let wincount = winnr('$')
+  exe 'terminal' &shell &shellcmdflag 'exit'
+  let job = term_getjob(bufnr())
+  call WaitForAssert({-> assert_equal("dead", job_status(job))})
+
+  let old_wincolor = &wincolor
+  try
+    set wincolor=
+  finally
+    let &wincolor = old_wincolor
+    bw!
+  endtry
+endfunc

src/version.c

@@ -742,6 +742,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    237,
 /**/
     236,
 /**/