Coverity analysis defect 72413: Resource leak

A new defect has been detected and assigned to charlie.swanson in Coverity Connect.
http://coverity.mongodb.com//sourcebrowser.htm?projectId=10001#mergedDefectId=72413
The defect was flagged by checker RESOURCE_LEAK in
file /src/mongo/db/query/query_planner.cpp
function mongo::QueryPlanner::planFromCache(const mongo::CanonicalQuery &, const mongo::QueryPlannerParams &, const mongo::CachedSolution &, mongo::QuerySolution **)
and this ticket was created by charlie.swanson