fix: input message should be trimmed before check if it is empty.

[yanCode]

blank spaces shouldn't be allowed to submitted as messages. original logic only avoid 0-length messages, but failed to stop blank space messages.

原来逻辑可以阻止用户不输入的情况下不能提交消息，但是用户输入空格之后，还是可以提交空格消息