Fix for fparser optimization with NaN
Fix for fparser optimization with NaN

This probably isn't the only place where the optimizer is implicitly
assuming that values aren't NaN, but it's the only one I could find
and it's sufficient to fix my test case.

vikramvgarg/libmesh,dschwen/libmesh,roystgnr/libmesh,dschwen/libmesh,vikramvgarg/libmesh,BalticPinguin/libmesh,benkirk/libmesh,salazardetroya/libmesh,cahaynes/libmesh,dknez/libmesh,permcody/libmesh,jiangwen84/libmesh,pbauman/libmesh,karpeev/libmesh,svallaghe/libmesh,svallaghe/libmesh,BalticPinguin/libmesh,libMesh/libmesh,svallaghe/libmesh,Mbewu/libmesh,vikramvgarg/libmesh,capitalaslash/libmesh,salazardetroya/libmesh,BalticPinguin/libmesh,pbauman/libmesh,giorgiobornia/libmesh,hrittich/libmesh,cahaynes/libmesh,aeslaughter/libmesh,Mbewu/libmesh,libMesh/libmesh,roystgnr/libmesh,permcody/libmesh,Mbewu/libmesh,balborian/libmesh,friedmud/libmesh,BalticPinguin/libmesh,dmcdougall/libmesh,vikramvgarg/libmesh,hrittich/libmesh,permcody/libmesh,roystgnr/libmesh,karpeev/libmesh,cahaynes/libmesh,dschwen/libmesh,friedmud/libmesh,friedmud/libmesh,hrittich/libmesh,BalticPinguin/libmesh,giorgiobornia/libmesh,giorgiobornia/libmesh,permcody/libmesh,jwpeterson/libmesh,hrittich/libmesh,cahaynes/libmesh,hrittich/libmesh,aeslaughter/libmesh,coreymbryant/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,friedmud/libmesh,Mbewu/libmesh,libMesh/libmesh,Mbewu/libmesh,roystgnr/libmesh,pbauman/libmesh,dknez/libmesh,karpeev/libmesh,dmcdougall/libmesh,roystgnr/libmesh,karpeev/libmesh,svallaghe/libmesh,svallaghe/libmesh,coreymbryant/libmesh,dschwen/libmesh,giorgiobornia/libmesh,salazardetroya/libmesh,giorgiobornia/libmesh,balborian/libmesh,hrittich/libmesh,coreymbryant/libmesh,Mbewu/libmesh,permcody/libmesh,dschwen/libmesh,jwpeterson/libmesh,dmcdougall/libmesh,permcody/libmesh,jwpeterson/libmesh,friedmud/libmesh,Mbewu/libmesh,benkirk/libmesh,dknez/libmesh,salazardetroya/libmesh,jwpeterson/libmesh,vikramvgarg/libmesh,roystgnr/libmesh,capitalaslash/libmesh,friedmud/libmesh,cahaynes/libmesh,karpeev/libmesh,90jrong/libmesh,vikramvgarg/libmesh,karpeev/libmesh,dmcdougall/libmesh,cahaynes/libmesh,90jrong/libmesh,svallaghe/libmesh,pbauman/libmesh,giorgiobornia/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,pbauman/libmesh,pbauman/libmesh,hrittich/libmesh,roystgnr/libmesh,coreymbryant/libmesh,svallaghe/libmesh,libMesh/libmesh,dknez/libmesh,pbauman/libmesh,jiangwen84/libmesh,benkirk/libmesh,giorgiobornia/libmesh,dschwen/libmesh,permcody/libmesh,libMesh/libmesh,coreymbryant/libmesh,Mbewu/libmesh,benkirk/libmesh,karpeev/libmesh,dknez/libmesh,capitalaslash/libmesh,jiangwen84/libmesh,vikramvgarg/libmesh,balborian/libmesh,libMesh/libmesh,benkirk/libmesh,benkirk/libmesh,friedmud/libmesh,jwpeterson/libmesh,dmcdougall/libmesh,balborian/libmesh,libMesh/libmesh,salazardetroya/libmesh,friedmud/libmesh,coreymbryant/libmesh,permcody/libmesh,giorgiobornia/libmesh,aeslaughter/libmesh,hrittich/libmesh,libMesh/libmesh,jiangwen84/libmesh,capitalaslash/libmesh,balborian/libmesh,dmcdougall/libmesh,salazardetroya/libmesh,benkirk/libmesh,jiangwen84/libmesh,svallaghe/libmesh,dmcdougall/libmesh,balborian/libmesh,jiangwen84/libmesh,balborian/libmesh,jwpeterson/libmesh,aeslaughter/libmesh,friedmud/libmesh,90jrong/libmesh,giorgiobornia/libmesh,cahaynes/libmesh,aeslaughter/libmesh,pbauman/libmesh,benkirk/libmesh,BalticPinguin/libmesh,90jrong/libmesh,90jrong/libmesh,aeslaughter/libmesh,jiangwen84/libmesh,balborian/libmesh,dmcdougall/libmesh,90jrong/libmesh,dschwen/libmesh,90jrong/libmesh,salazardetroya/libmesh,90jrong/libmesh,roystgnr/libmesh,dschwen/libmesh,capitalaslash/libmesh,cahaynes/libmesh,balborian/libmesh,Mbewu/libmesh,salazardetroya/libmesh,coreymbryant/libmesh,vikramvgarg/libmesh,karpeev/libmesh,dknez/libmesh,svallaghe/libmesh,vikramvgarg/libmesh,capitalaslash/libmesh,dknez/libmesh,benkirk/libmesh,pbauman/libmesh,aeslaughter/libmesh,aeslaughter/libmesh,jwpeterson/libmesh,90jrong/libmesh,BalticPinguin/libmesh,coreymbryant/libmesh,dknez/libmesh,hrittich/libmesh,aeslaughter/libmesh,balborian/libmesh,jiangwen84/libmesh