patch 8.1.1433: win_execute() may leave popup window focused

Problem:    Win_execute() may leave popup window focused, eventually leading
            to a crash. (Bjorn Linse)
Solution:   When previous window was closed, go to the first window.

src/testdir/test_popupwin.vim

@@ -105,6 +105,14 @@ func Test_popup_with_syntax_setbufvar()
   call delete('XtestPopup')
 endfunc
 
+func Test_win_execute_closing_curwin()
+  split
+  let winid = popup_create('some text', {})
+  call win_execute(winid, winnr() .. "close")
+  call assert_equal(1, winnr())
+  popupclear
+endfunc
+
 func Test_popup_with_wrap()
   if !CanRunVimInTerminal()
     return

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1433,
 /**/
     1432,
 /**/

src/window.c

@@ -6573,6 +6573,12 @@ restore_win_noblock(
 	curwin = save_curwin;
 	curbuf = curwin->w_buffer;
     }
+#ifdef FEAT_TEXT_PROP
+    else if (bt_popup(curwin->w_buffer))
+	// original window was closed and now we're in a popup window: Go
+	// to the first valid window.
+	win_goto(firstwin);
+#endif
 }
 
 /*