go.tools/dashboard/app: don't ignore field mismatch errors
go.tools/dashboard/app: don't ignore field mismatch errors

This was a hold-over from when we removed install counts years ago.
All the Package entities are well-formed these days.

LGTM=dsymonds
R=dsymonds
CC=golang-codereviews
https://golang.org/cl/138620043

syreclabs/go-tools,cw2018/tools,maddyonline/tools,springning/tools,magiccao/tools,josharian/tools,sshetty10/tools,springning/tools,nicot/tools,cmars/tools,nicot/tools,cw2018/tools,nicot/tools,glasser/golang-tools,josharian/tools,matryer/tools,syreclabs/go-tools,dmitris/tools,jdhenke/tools,runcom/tools,golang/tools,cmars/tools,runcom/tools,syreclabs/go-tools,magiccao/tools,jdhenke/tools,matryer/tools,maddyonline/tools,josharian/tools,argandas/tools,sshetty10/tools,golang/tools,4ad/tools,maddyonline/tools,jdhenke/tools,matryer/tools,golang/tools,glasser/golang-tools,cmars/tools,cmars/tools,magiccao/tools,golang/tools,syreclabs/go-tools,springning/tools,josharian/tools,matryer/tools,dmitris/tools,nicot/tools,argandas/tools,sshetty10/tools,maddyonline/tools,springning/tools,golang/tools,runcom/tools,jdhenke/tools,cw2018/tools,syreclabs/go-tools,argandas/tools,magiccao/tools,syreclabs/go-tools,argandas/tools,4ad/tools,4ad/tools,dmitris/tools,sshetty10/tools,runcom/tools,glasser/golang-tools,cw2018/tools,glasser/golang-tools,dmitris/tools