Fix TypeError in _nonNegativeDelta when val is None and maxValue is set#2912

deniszh merged 2 commits into

graphite-project:mastergraphite-project/graphite-web:masterfrom

npazosmendez:njpm/fix-non-negative-delta-none-valnpazosmendez/graphite-web:njpm/fix-non-negative-delta-none-valCopy head branch name to clipboard