Made alt_txn_t constructor handle preceding_txn being NULL.
Made alt_txn_t constructor handle preceding_txn being NULL.

scripni/rethinkdb,JackieXie168/rethinkdb,urandu/rethinkdb,lenstr/rethinkdb,bchavez/rethinkdb,pap/rethinkdb,gdi2290/rethinkdb,dparnell/rethinkdb,bpradipt/rethinkdb,greyhwndz/rethinkdb,AntouanK/rethinkdb,Wilbeibi/rethinkdb,eliangidoni/rethinkdb,spblightadv/rethinkdb,Wilbeibi/rethinkdb,elkingtonmcb/rethinkdb,mbroadst/rethinkdb,greyhwndz/rethinkdb,yakovenkodenis/rethinkdb,robertjpayne/rethinkdb,bchavez/rethinkdb,ayumilong/rethinkdb,KSanthanam/rethinkdb,Qinusty/rethinkdb,losywee/rethinkdb,robertjpayne/rethinkdb,JackieXie168/rethinkdb,gavioto/rethinkdb,wujf/rethinkdb,Wilbeibi/rethinkdb,KSanthanam/rethinkdb,victorbriz/rethinkdb,losywee/rethinkdb,Wilbeibi/rethinkdb,Qinusty/rethinkdb,grandquista/rethinkdb,tempbottle/rethinkdb,losywee/rethinkdb,marshall007/rethinkdb,jmptrader/rethinkdb,grandquista/rethinkdb,urandu/rethinkdb,sbusso/rethinkdb,matthaywardwebdesign/rethinkdb,mbroadst/rethinkdb,bpradipt/rethinkdb,wkennington/rethinkdb,scripni/rethinkdb,dparnell/rethinkdb,spblightadv/rethinkdb,victorbriz/rethinkdb,JackieXie168/rethinkdb,spblightadv/rethinkdb,4talesa/rethinkdb,KSanthanam/rethinkdb,ajose01/rethinkdb,yaolinz/rethinkdb,yakovenkodenis/rethinkdb,AntouanK/rethinkdb,wkennington/rethinkdb,victorbriz/rethinkdb,sontek/rethinkdb,losywee/rethinkdb,mcanthony/rethinkdb,jesseditson/rethinkdb,mbroadst/rethinkdb,gavioto/rethinkdb,sontek/rethinkdb,RubenKelevra/rethinkdb,mquandalle/rethinkdb,alash3al/rethinkdb,rrampage/rethinkdb,sontek/rethinkdb,bchavez/rethinkdb,scripni/rethinkdb,dparnell/rethinkdb,robertjpayne/rethinkdb,bchavez/rethinkdb,niieani/rethinkdb,rrampage/rethinkdb,ayumilong/rethinkdb,RubenKelevra/rethinkdb,gavioto/rethinkdb,jmptrader/rethinkdb,tempbottle/rethinkdb,marshall007/rethinkdb,Wilbeibi/rethinkdb,sebadiaz/rethinkdb,robertjpayne/rethinkdb,wojons/rethinkdb,catroot/rethinkdb,wujf/rethinkdb,RubenKelevra/rethinkdb,marshall007/rethinkdb,victorbriz/rethinkdb,yaolinz/rethinkdb,grandquista/rethinkdb,bpradipt/rethinkdb,4talesa/rethinkdb,AntouanK/rethinkdb,mquandalle/rethinkdb,JackieXie168/rethinkdb,sbusso/rethinkdb,yakovenkodenis/rethinkdb,sebadiaz/rethinkdb,lenstr/rethinkdb,gdi2290/rethinkdb,wkennington/rethinkdb,captainpete/rethinkdb,AntouanK/rethinkdb,Qinusty/rethinkdb,ajose01/rethinkdb,bpradipt/rethinkdb,losywee/rethinkdb,urandu/rethinkdb,JackieXie168/rethinkdb,sontek/rethinkdb,niieani/rethinkdb,marshall007/rethinkdb,bpradipt/rethinkdb,marshall007/rethinkdb,bpradipt/rethinkdb,bchavez/rethinkdb,dparnell/rethinkdb,JackieXie168/rethinkdb,Qinusty/rethinkdb,yaolinz/rethinkdb,captainpete/rethinkdb,greyhwndz/rethinkdb,marshall007/rethinkdb,sebadiaz/rethinkdb,elkingtonmcb/rethinkdb,tempbottle/rethinkdb,wkennington/rethinkdb,niieani/rethinkdb,Qinusty/rethinkdb,4talesa/rethinkdb,catroot/rethinkdb,JackieXie168/rethinkdb,greyhwndz/rethinkdb,mquandalle/rethinkdb,rrampage/rethinkdb,bchavez/rethinkdb,ayumilong/rethinkdb,gavioto/rethinkdb,wkennington/rethinkdb,mquandalle/rethinkdb,elkingtonmcb/rethinkdb,ajose01/rethinkdb,yakovenkodenis/rethinkdb,greyhwndz/rethinkdb,KSanthanam/rethinkdb,yaolinz/rethinkdb,captainpete/rethinkdb,mcanthony/rethinkdb,jesseditson/rethinkdb,4talesa/rethinkdb,mcanthony/rethinkdb,Qinusty/rethinkdb,KSanthanam/rethinkdb,AntouanK/rethinkdb,eliangidoni/rethinkdb,mbroadst/rethinkdb,ajose01/rethinkdb,sbusso/rethinkdb,sbusso/rethinkdb,wujf/rethinkdb,pap/rethinkdb,ajose01/rethinkdb,catroot/rethinkdb,tempbottle/rethinkdb,bpradipt/rethinkdb,mcanthony/rethinkdb,sbusso/rethinkdb,bchavez/rethinkdb,robertjpayne/rethinkdb,sbusso/rethinkdb,greyhwndz/rethinkdb,ajose01/rethinkdb,rrampage/rethinkdb,scripni/rethinkdb,sebadiaz/rethinkdb,jesseditson/rethinkdb,victorbriz/rethinkdb,JackieXie168/rethinkdb,elkingtonmcb/rethinkdb,rrampage/rethinkdb,sebadiaz/rethinkdb,mquandalle/rethinkdb,victorbriz/rethinkdb,wojons/rethinkdb,lenstr/rethinkdb,grandquista/rethinkdb,matthaywardwebdesign/rethinkdb,jesseditson/rethinkdb,yakovenkodenis/rethinkdb,gdi2290/rethinkdb,wojons/rethinkdb,marshall007/rethinkdb,urandu/rethinkdb,sontek/rethinkdb,mcanthony/rethinkdb,alash3al/rethinkdb,jmptrader/rethinkdb,scripni/rethinkdb,sebadiaz/rethinkdb,urandu/rethinkdb,bchavez/rethinkdb,jesseditson/rethinkdb,eliangidoni/rethinkdb,mbroadst/rethinkdb,pap/rethinkdb,alash3al/rethinkdb,yaolinz/rethinkdb,mcanthony/rethinkdb,alash3al/rethinkdb,wojons/rethinkdb,AntouanK/rethinkdb,dparnell/rethinkdb,Wilbeibi/rethinkdb,mquandalle/rethinkdb,jmptrader/rethinkdb,urandu/rethinkdb,alash3al/rethinkdb,spblightadv/rethinkdb,4talesa/rethinkdb,ayumilong/rethinkdb,niieani/rethinkdb,AntouanK/rethinkdb,bchavez/rethinkdb,gdi2290/rethinkdb,wkennington/rethinkdb,RubenKelevra/rethinkdb,dparnell/rethinkdb,eliangidoni/rethinkdb,catroot/rethinkdb,matthaywardwebdesign/rethinkdb,yakovenkodenis/rethinkdb,victorbriz/rethinkdb,sontek/rethinkdb,niieani/rethinkdb,eliangidoni/rethinkdb,grandquista/rethinkdb,pap/rethinkdb,lenstr/rethinkdb,wkennington/rethinkdb,gdi2290/rethinkdb,tempbottle/rethinkdb,jesseditson/rethinkdb,catroot/rethinkdb,eliangidoni/rethinkdb,4talesa/rethinkdb,rrampage/rethinkdb,ma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