[math] fix leak in GussLegendreIntegrator
[math] fix leak in GussLegendreIntegrator

If CalcGaussLegendreSamplingPoints() called many time, internal
temporary buffer was never released
olifre/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,karies/root,root-mirror/root,karies/root,root-mirror/root,karies/root,olifre/root,karies/root,olifre/root,karies/root,karies/root,root-mirror/root,olifre/root,karies/root,olifre/root,karies/root,olifre/root,olifre/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root