Fix valgrind warnings in -[TreeIndex initIterator]
Fix valgrind warnings in -[TreeIndex initIterator]

Fix a valgrind warning in sptree.h discovered by new tests.

ocelot-inc/tarantool,vasilenkomike/tarantool,rtsisyk/tarantool,mejedi/tarantool,guard163/tarantool,condor-the-bird/tarantool,Sannis/tarantool,guard163/tarantool,nvoron23/tarantool,KlonD90/tarantool,KlonD90/tarantool,KlonD90/tarantool,dkorolev/tarantool,ocelot-inc/tarantool,nvoron23/tarantool,mejedi/tarantool,rtsisyk/tarantool,dkorolev/tarantool,nvoron23/tarantool,guard163/tarantool,rtsisyk/tarantool,ocelot-inc/tarantool,condor-the-bird/tarantool,rtsisyk/tarantool,vasilenkomike/tarantool,condor-the-bird/tarantool,dkorolev/tarantool,nvoron23/tarantool,nvoron23/tarantool,dkorolev/tarantool,KlonD90/tarantool,condor-the-bird/tarantool,ocelot-inc/tarantool,KlonD90/tarantool,condor-the-bird/tarantool,vasilenkomike/tarantool,dkorolev/tarantool,Sannis/tarantool,guard163/tarantool,nvoron23/tarantool,mejedi/tarantool,guard163/tarantool,vasilenkomike/tarantool,vasilenkomike/tarantool,mejedi/tarantool,Sannis/tarantool,Sannis/tarantool,Sannis/tarantool