Don't crash heart if doctor isn't registered yet.
Don't crash heart if doctor isn't registered yet.

Change-Id: I9e3985679b2aef2a6cdb27ab7fa5c19bf23d773c
Reviewed-on: http://review.northscale.com/2541
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

t3rm1n4l/ns_server,vzasade/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,membase/ns_server,daverigby/ns_server,nimishzynga/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,ceejatec/ns_server,vzasade/ns_server,daverigby/ns_server,mschoch/ns_server,membase/ns_server,daverigby/ns_server,mschoch/ns_server,mschoch/ns_server,nimishzynga/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,mschoch/ns_server,daverigby/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,membase/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,vzasade/ns_server,ceejatec/ns_server