Kunna slang

In a book i'm reading a sentence uses the word kunna.

Mousugu kurisumasu da iu noni nandaka kunna youki da na.

My interpretation is:

Although it's almost christmas I'm somewhat not cheerful.

Is this kunna a slang pattern of nakunatta and if so is it used often?

なんだかくんなようき "nandaka kunna youki" doesn't make sense at all. I highly doubt it would be a misread/typo of なんだかへんなようき（＝変な陽気）"nandaka henna youki".