Fix the problem with zero weights

[segasai]

fix the problem when some weights are zero and the required number of points can't be selected

[coveralls]

Pull Request Test Coverage Report for Build 886435600

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.02%) to 71.646%

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Totals
Change from base Build 883214612:	-0.02%
Covered Lines:	3338
Relevant Lines:	4659

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💛 - Coveralls