fix Mustache(Mu) crash when finding a 'null' value (cherry picked from commit 5f5599406a84c6a839a2d0add9c37ea8205421fc)
fix Mustache(Mu) crash when finding a 'null' value
(cherry picked from commit 5f5599406a84c6a839a2d0add9c37ea8205421fc)

1950195/mojito,1950195/mojito,jeffblack360/mojito,ooskapenaar/mojito,jeffblack360/mojito,yahoo/mojito,jeffblack360/mojito,yahoo/mojito,ooskapenaar/mojito,yahoo/mojito,ooskapenaar/mojito,1950195/mojito,jeffblack360/mojito,ooskapenaar/mojito