Bugfix to prevent AttributeError when checking various command line a…

[crimsonkissaki]

…rguments.

This fixes errors when attempting to use list & search subparsers.

$ garden search contextmenu
[INFO ] [Logger ] Record log in C:\Users\Minion.kivy\logs\kivy_17-05-05_34.txt
[INFO ] [Kivy ] v1.9.1
[INFO ] [Python ] v3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 17:54:52) [MSC v.1900 32 bi t (Intel)]
Traceback (most recent call last):
File "C:/Software/Python/Python36-32/Scripts/garden", line 224, in
GardenTool().main(sys.argv[1:])
File "C:/Software/Python/Python36-32/Scripts/garden", line 82, in main
options.package = [p.lower() for p in options.package]
AttributeError: 'Namespace' object has no attribute 'package'