patch 8.2.0117: crash when using gettabwinvar() with invalid arguments

Problem:    Crash when using gettabwinvar() with invalid arguments. (Yilin
            Yang)
Solution:   Use "curtab" if "tp" is NULL. (closes #5475)
diff --git a/src/evalwindow.c b/src/evalwindow.c
index 672bfc1..fb54033 100644
--- a/src/evalwindow.c
+++ b/src/evalwindow.c
@@ -183,7 +183,8 @@
     {
 #ifdef FEAT_PROP_POPUP
 	// check tab-local popup windows
-	for (wp = tp->tp_first_popupwin; wp != NULL; wp = wp->w_next)
+	for (wp = (tp == NULL ? curtab : tp)->tp_first_popupwin;
+						   wp != NULL; wp = wp->w_next)
 	    if (wp->w_id == nr)
 		return wp;
 	// check global popup windows
diff --git a/src/testdir/test_getvar.vim b/src/testdir/test_getvar.vim
index 5a96548..5da5991 100644
--- a/src/testdir/test_getvar.vim
+++ b/src/testdir/test_getvar.vim
@@ -83,6 +83,7 @@
 
   unlet def_dict
 
+  call assert_equal("", gettabwinvar(9, 2020, ''))
   call assert_equal('', gettabwinvar(2, 3, '&nux'))
   call assert_equal(1, gettabwinvar(2, 3, '&nux', 1))
   tabonly
diff --git a/src/version.c b/src/version.c
index 1e79e03..25049a0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    117,
+/**/
     116,
 /**/
     115,