add check for missing game record
add check for missing game record

If a user attempts to view a game detail that has no associated game record
(i.e. SGF file), then report the missing record rather than raising an
exception.

Signed-off-by: Tim Henigan <87cde53fee35ccd1f5f73fcc5c91a1926c74a61a@gmail.com>

usgo/online-ratings,duckpunch/online-ratings,duckpunch/online-ratings,Kashomon/online-ratings,usgo/online-ratings,Kashomon/online-ratings,Kashomon/online-ratings,usgo/online-ratings