Incorrect variable reference in param.image alpha

[ncammarata]

No description provided.

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[ncammarata]

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[coveralls]

Pull Request Test Coverage Report for Build 560

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 70.435%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lucid/optvis/param/images.py	0	1	0.0%

Totals
Change from base Build 558:	0.0%
Covered Lines:	1763
Relevant Lines:	2503

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💛 - Coveralls