patch 9.1.1041: Vim9: out-of-bound access when echoing an enum

Problem:  Vim9: out-of-bound access when echoing an enum
Solution: Add NUL to growarray, check that ufunc is non-null
          before accessing it to make Coverity happy
          (Yegappan Lakshmanan)

closes: #16488

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/vim9expr.c b/src/vim9expr.c
index 7b8c96a..b765448 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -406,7 +406,7 @@
 	    }
 	}
 
-	if (is_super && IS_ABSTRACT_METHOD(ufunc))
+	if (is_super && ufunc != NULL && IS_ABSTRACT_METHOD(ufunc))
 	{
 	    // Trying to invoke an abstract method in a super class is not
 	    // allowed.