Adding the relevant backtrace from the bug report -

#0  0x00000000 in ?? ()
No symbol table info available.
#1  0x00d89c6b in QObject::~QObject (this=0x8e54768, __in_chrg=<optimized out>) at kernel/qobject.cpp:861
        d = 0x8e63208
#2  0x00d8a2a2 in QObject::~QObject (this=0x8e54768, __in_chrg=<optimized out>) at kernel/qobject.cpp:964
No locals.
#3  0x0804b409 in signalHandler (signal=<optimized out>) at ../../../nepomuk/servicestub/main.cpp:49
No locals.
#4  (anonymous namespace)::signalHandler (signal=1) at ../../../nepomuk/servicestub/main.cpp:43
No locals.
#5  <signal handler called>
No symbol table info available.
#6  0x00bdf416 in __kernel_vsyscall ()
No symbol table info available.
#7  0x004c7a5c in pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:169
No locals.
#8  0x0077dd4c in __pthread_cond_wait (cond=0x8e6f948, mutex=0x8e6f930) at forward.c:139
        __p = <optimized out>
#9  0x00c76a50 in wait (time=4294967295, this=0x8e6f930) at thread/qwaitcondition_unix.cpp:88
        code = <optimized out>
#10 QWaitCondition::wait (this=0x8eb90d8, mutex=0x8eb90c0, time=4294967295) at thread/qwaitcondition_unix.cpp:160
        returnValue = false
#11 0x00c76205 in QThread::wait (this=0x8e71bb8, time=4294967295) at thread/qthread_unix.cpp:745
        d = 0x8eb9070
        locker = {val = 149655745}
#12 0x0254c4a0 in Nepomuk::FileIndexer::~FileIndexer (this=0x8e12190, __in_chrg=<optimized out>) at ../../../../nepomuk/services/fileindexer/fileindexer.cpp:106
No locals.
#13 0x0254c4f2 in Nepomuk::FileIndexer::~FileIndexer (this=0x8e12190, __in_chrg=<optimized out>) at ../../../../nepomuk/services/fileindexer/fileindexer.cpp:109
No locals.
#14 0x00d854a1 in QObjectPrivate::deleteChildren (this=0x8e63208) at kernel/qobject.cpp:1955
        i = <optimized out>
        reallyWasDeleted = true
#15 0x00d8a099 in QObject::~QObject (this=0x8e54768, __in_chrg=<optimized out>) at kernel/qobject.cpp:946
        d = 0x8e63208
#16 0x0804bb60 in Nepomuk::ServiceControl::~ServiceControl (this=0x8e54768, __in_chrg=<optimized out>) at ../../../nepomuk/servicestub/servicecontrol.cpp:42
No locals.
#17 0x00d854a1 in QObjectPrivate::deleteChildren (this=0x8db22e8) at kernel/qobject.cpp:1955
        i = <optimized out>
        reallyWasDeleted = true
#18 0x00d8a099 in QObject::~QObject (this=0xbf9637e4, __in_chrg=<optimized out>) at kernel/qobject.cpp:946
        d = 0x8db22e8
#19 0x00d742a8 in QCoreApplication::~QCoreApplication (this=0xbf9637e4, __in_chrg=<optimized out>) at kernel/qcoreapplication.cpp:671
No locals.
#20 0x00fe6cc3 in QApplication::~QApplication (this=0xbf9637e4, __in_chrg=<optimized out>) at kernel/qapplication.cpp:1093
No locals.
#21 0x0804b0c1 in main (argc=2, argv=0xbf963974) at ../../../nepomuk/servicestub/main.cpp:168
        aboutData = {d = 0x8d9b440}
        serviceName = {static null = {<No data fields>}, static shared_null = {ref = {_q_value = 1}, alloc = 0, size = 0, data = 0x804f272, clean = 0, simpletext = 0, righttoleft = 0, asciiCache = 0, capacity = 0, reserved = 0, array = {0}}, static shared_empty = {ref = {_q_value = 43}, alloc = 0, size = 0, data = 0xea849e, clean = 0, simpletext = 0, righttoleft = 0, asciiCache = 0, capacity = 0, reserved = 0, array = {0}}, d = 0x8dae6f0, static codecForCStrings = 0x0}
        component = {_vptr.KComponentData = 0x3d1700, d = 0x8dae738}
        app = {<QCoreApplication> = {<QObject> = {_vptr.QObject = 0xea6128, static staticMetaObject = {d = {superdata = 0x0, stringdata = 0xe331e0 "QObject", data = 0xe33280, extradata = 0xea23a0}}, d_ptr = {d = 0x8db22e8}, static staticQtMetaObject = {d = {superdata = 0x0, stringdata = 0xe3bd40 "Qt", data = 0xe3f5e0, extradata = 0x0}}}, static staticMetaObject = {d = {superdata = 0x804f1d0, stringdata = 0xe45580 "QCoreApplication", data = 0xe45620, extradata = 0x0}}, static self = 0x0}, static staticMetaObject = {d = {superdata = 0xea74e0, stringdata = 0x1700420 "QApplication", data = 0x1700660, extradata = 0x0}}}
        dependencies = {<QList<QString>> = {{p = {static shared_null = {ref = {_q_value = 1}, alloc = 0, begin = 0, end = 0, sharable = 1, array = {0x0}}, d = 0x804f290}, d = 0x804f290}}, <No data fields>}
        __PRETTY_FUNCTION__ = "int main(int, char**)"
        options = {d = 0x8d9ba30}
        args = <optimized out>
        s = {_vptr.QTextStream = 0xea58c8, d_ptr = {d = 0x8dae058}}
        services = {{p = {static shared_null = {ref = {_q_value = 1}, alloc = 0, begin = 0, end = 0, sharable = 1, array = {0x0}}, d = 0x8e633b8}, d = 0x8e633b8}}
        service = {d = 0x8e4c708}

Fixed with 4.10.

We no longer have the IndexScheduler in a different thread.