Fix: Cannot read property 'removeChild' of undefined

[papandreou]

Fixes Munter/netlify-plugin-subfont#32

[coveralls]

Pull Request Test Coverage Report for Build 324

• 5 of 5 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 89.307%

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Totals
Change from base Build 320:	0.03%
Covered Lines:	993
Relevant Lines:	1064

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💛 - Coveralls

[Munter]

Great find!