Fix early return inside for loop

[papandreou]

Context: https://gitter.im/assetgraph/assetgraph?at=5dbb6438a3f0b17849c488cf

The bug is that we exit out of subsetFonts as soon as we encounter one page without any subset font usages. However, we're in a for loop, so we want to proceed with the remaining pages instead :)

[coveralls]

Pull Request Test Coverage Report for Build 205

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.3%) to 89.064%

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Files with Coverage Reduction	New Missed Lines	%
lib/subsetFonts.js	1	96.67%
lib/HeadlessBrowser.js	2	91.43%

Totals
Change from base Build 193:	-0.3%
Covered Lines:	1914
Relevant Lines:	2052

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💛 - Coveralls

[Munter]

Awesome. We probably need to lock this one down with a test, since it was so surprising

[papandreou]

I think it's unlikely to re-occur in this exact form, but I added a regression test now. Should also reclaim the lost coverage 😼

[Munter]

Awesone

[Munter]

Released in /~https://github.com/Munter/subfont/releases/tag/v4.0.2