Previously, using incorrect syntax for one of image, iframe, or video
functions caused an index out of range panic. Add a check to prevent
the panic and return an error instead.
Fixesgolang/go#35142
Change-Id: Ifffb4cc5daded5331d617a3db7cad84e37abadc8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/203477
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
Godoc depends on go.talks/pkg/present by way of go.tools/pkg/blog.
Better to keep all godoc dependencies in one place.
R=golang-dev, dsymonds, r
CC=golang-dev
https://golang.org/cl/13656047