Fix bugs in root isolation and refinement.
Fix bugs in root isolation and refinement.

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