patch 8.2.4661: Coverity warning for using uninitialized variable

Problem:    Coverity warning for using uninitialized variable.
Solution:   Initialize variable to NULL.
diff --git a/src/vim9expr.c b/src/vim9expr.c
index 9c18994..1b4c7b8 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -272,7 +272,7 @@
 	char_u	*p = skipwhite(*end);
 	char_u	*exp_name;
 	int	cc;
-	ufunc_T	*ufunc;
+	ufunc_T	*ufunc = NULL;
 	type_T	*type;
 	int	done = FALSE;
 	int	res = OK;