patch 9.1.1230: inconsistent CTRL-C behaviour for popup windows

Problem:  Ctrl-C closes popup windows that have a filter callback,
          but does not close popups without a filter callback.
Solution: Modified popup_do_filter() to also close popups without
          filter callback when Ctrl-C is pressed (glepnir).

fixes: #16839
closes: #16928

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index e1041ef..5082676 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -3898,6 +3898,24 @@
   call assert_equal({}, popup_getpos(win3))
 endfunc
 
+func Test_popupwin_cancel_with_without_filter()
+  let win1 = popup_create('with filter', #{line: 5, filter: {... -> 0}})
+  let win2 = popup_create('no filter', #{line: 10})
+
+  call assert_equal(5, popup_getpos(win1).line)
+  call assert_equal(10, popup_getpos(win2).line)
+
+  call feedkeys("\<C-C>", 'xt')
+  call assert_equal({}, popup_getpos(win1))
+  call assert_equal(10, popup_getpos(win2).line)
+
+  call feedkeys("\<C-C>", 'xt')
+  call assert_equal({}, popup_getpos(win1))
+  call assert_equal({}, popup_getpos(win2))
+
+  call popup_clear()
+endfunc
+
 func Test_popupwin_filter_redraw()
   " Create two popups with a filter that closes the popup when typing "0".
   " Both popups should close, even though the redraw also calls