Fixed product images fallback for variants without own images

[fkloes]

Description

This ticket is about to fix the product images fallback for product variants without images. In that case a gallery of the base product images should be shown if it has multiple images.

Type of change

• Bug Fix 🐛 (non-breaking change which fixes an issue)
• New Feature 🚀 (non-breaking change which adds functionality)
• Breaking Change 💥 (fix or feature that would cause existing functionality to not work as expected)
• Polish 💅 (Just some cleanups)
• Docs 📝 (Changes in the documentations)
• Internal 🏠 Only relates to internal processes.

How to test it

• put a variant without own images into the cart
• goto the cart and reload the page
• open the product within the cart

Desired outcome:
You see a product image gallery with the images of the parent product.

[coveralls]

Pull Request Test Coverage Report for Build 1715

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.004%) to 47.13%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
libraries/commerce/product/subscriptions/index.js	0	1	0.0%

Totals
Change from base Build 1714:	-0.004%
Covered Lines:	4843
Relevant Lines:	9705

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💛 - Coveralls