patch 9.0.1136: memory leak when getting class member type from expr

Problem:    Memory leak when getting class member type from expr.
Solution:   Clear the expression result.
diff --git a/src/vim9class.c b/src/vim9class.c
index e764f70..2717a79 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -99,8 +99,11 @@
 	    int res = eval0(expr, &tv, eap, &evalarg);
 
 	    if (res == OK)
+	    {
 		type = typval2type(&tv, get_copyID(), type_list,
 						       TVTT_DO_MEMBER);
+		clear_tv(&tv);
+	    }
 	    if (type == NULL)
 	    {
 		semsg(_(e_cannot_get_object_member_type_from_initializer_str),