www: prevent exception if a derived query base object is unknown
www: prevent exception if a derived query base object is unknown

nrc/dxr,pombredanne/dxr,pelmers/dxr,jonasfj/dxr,erikrose/dxr,gartung/dxr,pombredanne/dxr,jbradberry/dxr,kleintom/dxr,nrc/dxr,KiemVM/Mozilla--dxr,KiemVM/Mozilla--dxr,bozzmob/dxr,jonasfj/dxr,pelmers/dxr,KiemVM/Mozilla--dxr,erikrose/dxr,erikrose/dxr,bozzmob/dxr,KiemVM/Mozilla--dxr,pelmers/dxr,jay-z007/dxr,nrc/dxr,gartung/dxr,kleintom/dxr,bozzmob/dxr,erikrose/dxr,bozzmob/dxr,srenatus/dxr,jbradberry/dxr,nrc/dxr,srenatus/dxr,jay-z007/dxr,nrc/dxr,jay-z007/dxr,kleintom/dxr,gartung/dxr,pelmers/dxr,KiemVM/Mozilla--dxr,pombredanne/dxr,jbradberry/dxr,gartung/dxr,gartung/dxr,gartung/dxr,kleintom/dxr,jonasfj/dxr,srenatus/dxr,jay-z007/dxr,kleintom/dxr,srenatus/dxr,jonasfj/dxr,kleintom/dxr,jay-z007/dxr,pombredanne/dxr,srenatus/dxr,jbradberry/dxr,jbradberry/dxr,srenatus/dxr,kleintom/dxr,bozzmob/dxr,bozzmob/dxr,jbradberry/dxr,pelmers/dxr,jay-z007/dxr,jbradberry/dxr,jonasfj/dxr,nrc/dxr,jonasfj/dxr,pombredanne/dxr,pelmers/dxr,pombredanne/dxr,erikrose/dxr,gartung/dxr,pelmers/dxr,bozzmob/dxr,KiemVM/Mozilla--dxr,jay-z007/dxr,pombredanne/dxr