patch 8.2.0596: crash in test49

Problem:    Crash in test49.
Solution:   Check the right pointer.
diff --git a/src/userfunc.c b/src/userfunc.c
index 44118b1..dfda733 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2504,7 +2504,7 @@
 
 		// With Vim9 script the name was made script-local, if not
 		// found try again with the original name.
-		if (p != NULL)
+		if (up != NULL)
 		    fp = find_func(up, NULL);
 	    }