patch 9.0.1205: crash when handling class that extends another class

Problem:    Crash when handling class that extends another class with more
            than one object members.
Solution:   Correct pointer computations. (closes #11824)
diff --git a/src/vim9class.c b/src/vim9class.c
index 8dcd92b..1ead953 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -182,10 +182,11 @@
     for (int i = 0; i < parent_count; ++i)
     {
 	// parent members need to be copied
-	*members[i] = parent_members[i];
-	members[i]->ocm_name = vim_strsave(members[i]->ocm_name);
-	if (members[i]->ocm_init != NULL)
-	    members[i]->ocm_init = vim_strsave(members[i]->ocm_init);
+	ocmember_T	*m = *members + i;
+	*m = parent_members[i];
+	m->ocm_name = vim_strsave(m->ocm_name);
+	if (m->ocm_init != NULL)
+	    m->ocm_init = vim_strsave(m->ocm_init);
     }
     if (gap->ga_len > 0)
 	// new members are moved