patch 8.1.2109: popup_getoptions() hangs with tab-local popup

Problem:    popup_getoptions() hangs with tab-local popup.
Solution:   Correct pointer name. (Marko Mahnič, closes #5006)
diff --git a/src/popupwin.c b/src/popupwin.c
index a77d98b..0681207 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -2636,12 +2636,12 @@
 	i = 1;
 	FOR_ALL_TABPAGES(tp)
 	{
-	    win_T *p;
+	    win_T *twp;
 
-	     for (p = tp->tp_first_popupwin; p != NULL; p = wp->w_next)
-		 if (p->w_id == id)
+	     for (twp = tp->tp_first_popupwin; twp != NULL; twp = twp->w_next)
+		 if (twp->w_id == id)
 		     break;
-	     if (p != NULL)
+	     if (twp != NULL)
 		 break;
 	     ++i;
 	}