fix edit menu items

[chris48s]

Steps to reproduce bug:

• Start application
• Click any item in the Edit menu
• Application will throw ReferenceError: mainWindow is not defined

Looks like I broke this in PR #140 when I removed the mainWindow variable from the global scope but forgot to update these menu items. I think this is more correct anyway as previously these operations were probably being applied to whatever window was most recently created instead of the currently active window.

[Stephen-Gates]

Hi @chris48s, thanks for all your contributions. The ODI Australian Network has big plans for Comma Chameleon.
https://ask.theodi.org.au/t/a-vision-for-comma-chameleon/473

@pezholio pointed me in your direction.

Contact me via
Twitter @SGatesHQ
Email: StephenG @ ODIQueensland.org.au

to see the draft spec.

[quadrophobiac]

Hi @chris48s - thanks for working on this. I've confirmed that this patch fixes the majority of commands in the edit menu. The one exception is copy, for which I've opened a separate ticket #164 as I suspect its not related to the fix you've made here.
I'd also like to echo Stephen's sentiment - thanks so much for the consistent contributions to this repo! I wanted to let you know that you have push access on this repository, so you don't have to work in forks for any future contributions you'd like to make to this repository.