runtime: remove a redundant nil pointer check.
runtime: remove a redundant nil pointer check.

It appears this was made possible by commit 89f185f; before that, g was
not dereferenced above.

Change-Id: I70bc571d924b36351392fd4c13d681e938cfb573
Reviewed-on: https://go-review.googlesource.com/16033
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

goodlang/good,malvira/go,jacobsa/go,Cofyc/go,deft-code/go,suncycheng/go,fjballest/golang,linux-on-ibm-z/go,linux-on-ibm-z/go,josharian/go,rachtsingh/gogojuice,4ad/go,CAFxX/go,CAFxX/go,cyberroadie/go,dterei/go,kim-racktop/go,Jordanzuo/go,Samurais/go,binarycrusader/go,cloudflare/go,Endika/go,josharian/go,ImJasonH/go,binarycrusader/go,kim-racktop/go,Jordanzuo/go,vanloswang/go,sndnvaps/go,deft-code/go,sndnvaps/go,cloudflare/go,vanloswang/go,mwhudson/go,dterei/go,CAFxX/go,golang/go,cloudflare/go,binarycrusader/go,nawawi/go,deft-code/go,derekmarcotte/go,miolini/go,josharian/go,golang/go,suncycheng/go,sndnvaps/go,dterei/go,fjballest/golang,Cofyc/go,Samurais/go,vanloswang/go,theif519/go,Endika/go,theif519/go,Samurais/go,Cofyc/go,odeke-em/go,dterei/go,jacobsa/go,cloudflare/go,dterei/go,cloudflare/go,odeke-em/go,codestation/go,mwhudson/go,nawawi/go,josharian/go,ImJasonH/go,ganboing/go-esx,goodlang/good,polyverse-security/go,CAFxX/go,odeke-em/go,jacobsa/go,roth1002/go,sndnvaps/go,vsekhar/elastic-go,roth1002/go,golang/go,goodlang/good,Endika/go,nawawi/go,polyverse-security/go,4ad/go,jacobsa/go,sndnvaps/go,ganboing/go-esx,gdey/go,mwhudson/go,Jordanzuo/go,vanloswang/go,4ad/go,jacobsa/go,mwhudson/go,deft-code/go,Jordanzuo/go,rachtsingh/gogojuice,CAFxX/go,momchil-velikov/go,suncycheng/go,jacobsa/go,roth1002/go,sndnvaps/go,CAFxX/go,derekmarcotte/go,polyverse-security/go,akutz/go,codestation/go,vsekhar/elastic-go,codestation/go,momchil-velikov/go,binarycrusader/go,malvira/go,codestation/go,akutz/go,binarycrusader/go,cyberroadie/go,odeke-em/go,goodlang/good,ImJasonH/go,golang/go,fjballest/golang,rachtsingh/gogojuice,vsekhar/elastic-go,linux-on-ibm-z/go,codestation/go,vsekhar/elastic-go,mwhudson/go,suncycheng/go,nawawi/go,vanloswang/go,polyverse-security/go,cyberroadie/go,josharian/go,Cofyc/go,Endika/go,kim-racktop/go,vanloswang/go,ganboing/go-esx,Cofyc/go,derekmarcotte/go,malvira/go,ImJasonH/go,vsekhar/elastic-go,Jordanzuo/go,theif519/go,josharian/go,linux-on-ibm-z/go,codestation/go,golang/go,Endika/go,4ad/go,ImJasonH/go,derekmarcotte/go,binarycrusader/go,miolini/go,ganboing/go-esx,Samurais/go,kim-racktop/go,vanloswang/go,momchil-velikov/go,roth1002/go,ganboing/go-esx,ImJasonH/go,rachtsingh/gogojuice,theif519/go,linux-on-ibm-z/go,akutz/go,linux-on-ibm-z/go,vanloswang/go,roth1002/go,4ad/go,sndnvaps/go,fjballest/golang,goodlang/good,odeke-em/go,gdey/go,akutz/go,jacobsa/go,linux-on-ibm-z/go,akutz/go,CAFxX/go,Endika/go,odeke-em/go,Cofyc/go,CAFxX/go,odeke-em/go,derekmarcotte/go,cyberroadie/go,gdey/go,Jordanzuo/go,dterei/go,Endika/go,4ad/go,rachtsingh/gogojuice,cyberroadie/go,malvira/go,fjballest/golang,derekmarcotte/go,Endika/go,miolini/go,suncycheng/go,miolini/go,golang/go,Samurais/go,momchil-velikov/go,miolini/go,binarycrusader/go,sndnvaps/go,ImJasonH/go,momchil-velikov/go,cloudflare/go,deft-code/go,fjballest/golang,momchil-velikov/go,nawawi/go,Samurais/go,polyverse-security/go,derekmarcotte/go,malvira/go,cloudflare/go,Samurais/go,kim-racktop/go,suncycheng/go,fjballest/golang,gdey/go,deft-code/go,dterei/go,vsekhar/elastic-go,mwhudson/go,josharian/go,cyberroadie/go,malvira/go,akutz/go,roth1002/go,goodlang/good,Cofyc/go,akutz/go,christopher-henderson/Go,suncycheng/go,momchil-velikov/go,gdey/go,gdey/go,theif519/go,akutz/go,cyberroadie/go,cloudflare/go,binarycrusader/go,kim-racktop/go,malvira/go,momchil-velikov/go,theif519/go,nawawi/go,rachtsingh/gogojuice,goodlang/good,fjballest/golang,malvira/go,miolini/go,Jordanzuo/go,kim-racktop/go,golang/go,ganboing/go-esx,Jordanzuo/go,miolini/go,linux-on-ibm-z/go,odeke-em/go,Cofyc/go,josharian/go,vsekhar/elastic-go,ImJasonH/go,gdey/go,Samurais/go,roth1002/go,polyverse-security/go,codestation/go,vsekhar/elastic-go,nawawi/go,ganboing/go-esx,theif519/go,rachtsingh/gogojuice,jacobsa/go,mwhudson/go,cyberroadie/go,nawawi/go,suncycheng/go,mwhudson/go,gdey/go,miolini/go,derekmarcotte/go,roth1002/go,ganboing/go-esx,4ad/go,rachtsingh/gogojuice,goodlang/good,theif519/go,4ad/go,deft-code/go,deft-code/go,polyverse-security/go,polyverse-security/go,dterei/go,kim-racktop/go,codestation/go,golang/go