Tailcall handling fix when callstack is empty
Tailcall handling fix when callstack is empty

Caused some valgrind whines when callstack was empty, e.g. for initial
thread resume().

kphillisjr/duktape,harold-b/duktape,thurday/duktape,rwaldron/duktape,svaarala/duktape,eddieh/duktape,pombredanne/duktape,nivertech/duktape,haosu1987/duktape,nivertech/duktape,sloth4413/duktape,sloth4413/duktape,thurday/duktape,chenyaqiuqiu/duktape,reqshark/duktape,skomski/duktape,jmptrader/duktape,zeropool/duktape,pombredanne/duktape,harold-b/duktape,tassmjau/duktape,harold-b/duktape,chenyaqiuqiu/duktape,markand/duktape,kphillisjr/duktape,kphillisjr/duktape,reqshark/duktape,sloth4413/duktape,svaarala/duktape,harold-b/duktape,jmptrader/duktape,kphillisjr/duktape,svaarala/duktape,harold-b/duktape,markand/duktape,eddieh/duktape,rwaldron/duktape,markand/duktape,chenyaqiuqiu/duktape,daimajia/duktape,zeropool/duktape,markand/duktape,jmptrader/duktape,pombredanne/duktape,jmptrader/duktape,kphillisjr/duktape,reqshark/duktape,skomski/duktape,skomski/duktape,jmptrader/duktape,eddieh/duktape,pombredanne/duktape,kphillisjr/duktape,tassmjau/duktape,zeropool/duktape,harold-b/duktape,jmptrader/duktape,thurday/duktape,eddieh/duktape,pombredanne/duktape,markand/duktape,markand/duktape,tassmjau/duktape,markand/duktape,zeropool/duktape,pombredanne/duktape,skomski/duktape,tassmjau/duktape,tassmjau/duktape,chenyaqiuqiu/duktape,chenyaqiuqiu/duktape,harold-b/duktape,chenyaqiuqiu/duktape,nivertech/duktape,zeropool/duktape,tassmjau/duktape,harold-b/duktape,reqshark/duktape,tassmjau/duktape,nivertech/duktape,svaarala/duktape,haosu1987/duktape,skomski/duktape,daimajia/duktape,rwaldron/duktape,kphillisjr/duktape,sloth4413/duktape,nivertech/duktape,kphillisjr/duktape,thurday/duktape,zeropool/duktape,markand/duktape,eddieh/duktape,reqshark/duktape,nivertech/duktape,sloth4413/duktape,haosu1987/duktape,zeropool/duktape,tassmjau/duktape,chenyaqiuqiu/duktape,eddieh/duktape,zeropool/duktape,pombredanne/duktape,chenyaqiuqiu/duktape,skomski/duktape,skomski/duktape,thurday/duktape,rwaldron/duktape,daimajia/duktape,harold-b/duktape,reqshark/duktape,eddieh/duktape,pombredanne/duktape,sloth4413/duktape,harold-b/duktape,reqshark/duktape,thurday/duktape,eddieh/duktape,nivertech/duktape,jmptrader/duktape,kphillisjr/duktape,svaarala/duktape,haosu1987/duktape,rwaldron/duktape,daimajia/duktape,thurday/duktape,haosu1987/duktape,haosu1987/duktape,eddieh/duktape,chenyaqiuqiu/duktape,eddieh/duktape,nivertech/duktape,sloth4413/duktape,thurday/duktape,tassmjau/duktape,daimajia/duktape,svaarala/duktape,rwaldron/duktape,zeropool/duktape,sloth4413/duktape,thurday/duktape,nivertech/duktape,haosu1987/duktape,markand/duktape,jmptrader/duktape,markand/duktape,pombredanne/duktape,sloth4413/duktape,kphillisjr/duktape,reqshark/duktape,jmptrader/duktape,thurday/duktape,zeropool/duktape,svaarala/duktape,svaarala/duktape,reqshark/duktape,skomski/duktape,jmptrader/duktape,reqshark/duktape,chenyaqiuqiu/duktape,haosu1987/duktape,haosu1987/duktape,pombredanne/duktape,sloth4413/duktape,skomski/duktape,skomski/duktape,svaarala/duktape,haosu1987/duktape,tassmjau/duktape,nivertech/duktape,daimajia/duktape