Fix bug where fact(0) was returning 0 instead of 1.
Fix bug where fact(0) was returning 0 instead of 1.

JackSullivan/spire,AlecZorab/spire,tixxit/spire,rklaehn/spire,woparry/spire,adampingel/spire,guersam/spire,non/spire,AlecZorab/spire,JackSullivan/spire,kevinmeredith/spire,codeaudit/spire,adampingel/spire,rklaehn/spire,codeaudit/spire,non/spire,guersam/spire,woparry/spire,siddhartha-gadgil/spire,siddhartha-gadgil/spire,tixxit/spire,kevinmeredith/spire