Fix bugs with interval multiplication.
Fix bugs with interval multiplication.

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