Putting a space after certain commands which require no additional syntax gives a syntax error message when you type it in chat

If you type in "/help ", with the space after the world "help", the command help thingy says "Incorrect argument for command at position 5:" even though if you run the command it works normally. The same thing happens with /seed.

Steps to reproduce:

1. Type in "/help "
2. Notice the error message
3. Run the command
4. Notice it works.