app/build: fix JSON mode crash when viewing pages after the first
app/build: fix JSON mode crash when viewing pages after the first

Change-Id: I89e734d8fbb93b903de79cf4b4bce5693743a251
Reviewed-on: https://go-review.googlesource.com/9000
Reviewed-by: Austin Clements <7ea35d812706d9213868749011af1ed4fa2f6aa0@google.com>

golang/build,evandbrown/build,evandbrown/build,golang/build,golang/build,golang/build,proppy/build,proppy/build,evandbrown/build,proppy/build,proppy/build