Allow users to generate send tx offline

[summerxue1992]

You cannot build a transaction without a signed part on a node that is completely offline.When I build a transaction without a signature on a node without synchronized data,it prompts me to take the --node parameter.Connect to another node remotely to build the transaction,I think this goes against the definition of an offline signature.

[chengwenxi]

Thank you for rising this issue.

[haifengxi]

You have to be online to generate a tx, but can stay offline when signing it -- which is perfectly fine and safe. @summerxue1992

[chengwenxi]

This error occurred when creating transaction, will fix it.