Feature bug: progressT shows 100.0% completion for no tasks matched

[Jiacheng-y]

When the keyword for progressT does not match any labels, the task completion shows 100.0% completion instead of throwing a warning.

Steps to recreate situation: (using default data in YellowBook)

1. progressT cs2103t

The following result is shown:

100.0% task completion is quite misleading since the task labelled CS2103T is not actually completed, and the 100.0% was just because cs2103t did not match CS2103T. Perhaps showing users a warning that the keyword does not match any tasks will be more useful.