Fix potential issue with asynchronous function immediately after synchronous one
Fix potential issue with asynchronous function immediately after synchronous one

There could be the problem that no heartbeat interval was set when sending an
asynchronous function before the previous synchronous function responded.

#12 #14

peerigon/phridge,ad-venture/phridge,SystemParadox/phridge,SystemParadox/phridge,ad-venture/phridge,peerigon/phridge