Fix `fast_walk.cc` when there was an error
Fix `fast_walk.cc` when there was an error

In the error state, fast walk would just do an equality check instead of an assignment of the error. I'm an idiot :(
Gum-Joe/nodegit,jdgarcia/nodegit,jdgarcia/nodegit,nodegit/nodegit,jmurzy/nodegit,jmurzy/nodegit,Gum-Joe/nodegit,Gum-Joe/nodegit,nodegit/nodegit,jdgarcia/nodegit,jmurzy/nodegit,jmurzy/nodegit,jdgarcia/nodegit,Gum-Joe/nodegit,nodegit/nodegit,nodegit/nodegit,nodegit/nodegit,jmurzy/nodegit,jdgarcia/nodegit