go/ast: FuncType.Params may be nil (per AST documentation)
go/ast: FuncType.Params may be nil (per AST documentation)

ast.Walk needs to check for it or it will crash.

R=r
CC=golang-dev
http://codereview.appspot.com/6852062

mhennings/marcohennings-go,scirelli/scirelli-go,mhennings/marcohennings-go,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,rdp/rogerpack2005-golang,scirelli/scirelli-go,d0f/go-zh,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,webfd/go-zh,mhennings/marcohennings-go,d0f/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,mhennings/marcohennings-go,rdp/rogerpack2005-golang,scirelli/scirelli-go,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,bryanxu/go-zh,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,webfd/go-zh,mhennings/marcohennings-go,mhennings/marcohennings-go,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,bryanxu/go-zh,d0f/go-zh,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,bryanxu/go-zh,mhennings/marcohennings-go,scirelli/scirelli-go,bryanxu/go-zh,d0f/go-zh,rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,webfd/go-zh,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,d0f/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,d0f/go-zh,webfd/go-zh,rdp/rogerpack2005-golang,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,webfd/go-zh,rflanagan/reginaldflanagan-project1