No error message for entering empty command

[jevan13]

• Entering of empty command does not return any error message
• Should have one to notify users that it is an error, i.e. "Command cannot be empty"
• Error message remains from the previous command, as shown in the picture (i.e. it still shows the history error message)
• Causes inconvenience to users since the empty command is showing the history error message, and do not know the issue