[hack] Watchman no longer allows empty expression allof list. Omit if empty
[hack] Watchman no longer allows empty expression allof list. Omit if empty

Summary:
Informant-directed restarts were broken in the latest version of Watchman since the semantics
changed - watchman no longer allows an empty "allof" list for expressions.

This fixes that.

Reviewed By: jamesjwu

Differential Revision: D5305505

fbshipit-source-id: b04863bb6517a7d90fd8807492d21e975fad079f

nmote/flow,TiddoLangerak/flow,facebook/flow,JonathanUsername/flow,facebook/flow,gabelevi/flow,gabelevi/flow,jamesgpearce/flow,nmote/flow,mroch/flow,gabelevi/flow,JonathanUsername/flow,samwgoldman/flow,ylu1317/flow,JonathanUsername/flow,AgentME/flow,nmote/flow,jamesgpearce/flow,jamesgpearce/flow,popham/flow,mroch/flow,nmote/flow,claudiopro/flow,samwgoldman/flow,jamesgpearce/flow,ylu1317/flow,MichaelDeBoey/flow,JonathanUsername/flow,facebook/flow,mroch/flow,TiddoLangerak/flow,nmote/flow,claudiopro/flow,claudiopro/flow,MichaelDeBoey/flow,popham/flow,gabelevi/flow,ylu1317/flow,JonathanUsername/flow,JonathanUsername/flow,mroch/flow,gabelevi/flow,mroch/flow,nmote/flow,claudiopro/flow,mroch/flow,TiddoLangerak/flow,samwgoldman/flow,MichaelDeBoey/flow,jamesgpearce/flow,MichaelDeBoey/flow,samwgoldman/flow,facebook/flow,jamesgpearce/flow,MichaelDeBoey/flow,mroch/flow,claudiopro/flow,TiddoLangerak/flow,samwgoldman/flow,jamesgpearce/flow,popham/flow,facebook/flow,ylu1317/flow,facebook/flow,popham/flow,popham/flow,AgentME/flow,samwgoldman/flow,AgentME/flow,AgentME/flow,samwgoldman/flow,popham/flow,TiddoLangerak/flow,nmote/flow,JonathanUsername/flow,ylu1317/flow,popham/flow,AgentME/flow,gabelevi/flow,gabelevi/flow,facebook/flow