patch 8.1.1599: compiler warning for uninitialized variable

Problem:    Compiler warning for uninitialized variable. (Tony Mechelynck)
Solution:   Add a dummy assignment.
diff --git a/src/normal.c b/src/normal.c
index 5bd2e5e..0ab3db4 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -4560,9 +4560,9 @@
 	    nv_scroll_line(cap);
 	}
 #ifdef FEAT_TEXT_PROP
-	if (bt_popup(wp->w_buffer))
+	if (bt_popup(curwin->w_buffer))
 	{
-	    int	    height = wp->w_height;
+	    int	    height = curwin->w_height;
 
 	    curwin->w_firstline = curwin->w_topline;
 	    popup_adjust_position(curwin);