patch 9.1.1002: Vim9: unknown func error with interface declaring func var

Problem:  Vim9: unknown function error with interface declaring a
          function variable (lifepillar)
Solution: Use correct instruction for getting interface member variables
          (Yegappan Lakshmanan)

fixes: #16345
closes: #16421

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 cfdea7b..9a96034 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -392,8 +392,15 @@
 	    }
 	    else
 	    {
-		if (generate_GET_OBJ_MEMBER(cctx, m_idx, ocm->ocm_type) ==
-									FAIL)
+		int status;
+
+		if (IS_INTERFACE(cl))
+		    status = generate_GET_ITF_MEMBER(cctx, cl, m_idx,
+							ocm->ocm_type);
+		else
+		    status = generate_GET_OBJ_MEMBER(cctx, m_idx,
+							ocm->ocm_type);
+		if (status == FAIL)
 		    return FAIL;
 	    }
 	}