fix uninitialized field warnings

sql/handler.cc

@@ -2604,7 +2604,7 @@ static void xarecover_do_commit_or_rollback(handlerton *hton,
     // Populate xid using the server_id from original transaction
     x.set(member->xid, member->server_id);
   else
-    (XID)x= *member->full_xid;
+    x= *member->full_xid;
 
   rc= xarecover_decide_to_commit(member, ptr_commit_max) ?
     hton->commit_by_xid(hton, &x) : hton->rollback_by_xid(hton, &x);

sql/handler.h

@@ -978,6 +978,7 @@ struct Online_alter_cache_list;
 struct XA_data: XID
 {
   Online_alter_cache_list *online_alter_cache= NULL;
+  XA_data &operator=(const XID &x) { XID::operator=(x); return *this; }
 };
 
 /*

sql/rpl_record.cc

@@ -349,7 +349,7 @@ int unpack_row(const rpl_group_info *rgi, TABLE *table, uint const colcnt,
   st.next_null_byte();
   if (!rpl_data.is_online_alter())
   {
-    Field *result_field;
+    Field *result_field= NULL;
     for (; i < colcnt && (result_field= table->field[i]); i++)
     {
       /*