Wrong error message

[yuming7144]

Wrong error message is displayed when adding patients.
In the screenshot below, the add command was given a wrong format - the c/BlueViolet should be cr/BlueViolet. The prefix for color is wrong. An error message should be displayed stating the command is invalid. However, now it is complaining that "Allergy names should be alphanumeric", when my allergy is in the right format.

Steps to reproduce:

1. Enter the same command as shown in the screenshot.
2. An error message complaining about allergy field should appear. In particular, the message is "Allergy names should be alphanumeric".