(gdb) bt
#0  0x00005555558ba7b2 in SendCoinsDialog::updateCoinControlState (
    this=this@entry=0x55555833f710) at ./qt/sendcoinsdialog.cpp:850
#1  0x00005555558ba88e in SendCoinsDialog::updateSmartFeeLabel (
    this=0x55555833f710) at ./qt/sendcoinsdialog.cpp:863
#2  0x0000555556a99c3e in QObject::event(QEvent*) ()
#3  0x0000555555c4e603 in QApplicationPrivate::notify_helper(QObject*, QEvent*)
    ()
#4  0x0000555556a6829a in QCoreApplication::notifyInternal2(QObject*, QEvent*)
    ()
#5  0x0000555556a6c2bb in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) ()
#6  0x0000555556abfd45 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
#7  0x000055555636ae12 in QXcbUnixEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
#8  0x0000555556a66da6 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) ()
#9  0x0000555556a70128 in QCoreApplication::exec() ()
#10 0x00005555557bacda in GuiMain (argc=3, argv=0x7fffffffdff8)
    at ./qt/bitcoin.cpp:691
#11 0x00007ffff7867d90 in __libc_start_call_main (
    main=main@entry=0x55555573a580 <main(int, char**)>, argc=argc@entry=3,
    argv=argv@entry=0x7fffffffdff8)
    at ../sysdeps/nptl/libc_start_call_main.h:58
#12 0x00007ffff7867e40 in __libc_start_main_impl (
    main=0x55555573a580 <main(int, char**)>, argc=3, argv=0x7fffffffdff8,
    init=<optimised out>, fini=<optimised out>, rtld_fini=<optimised out>,
    stack_end=0x7fffffffdfe8) at ../csu/libc-start.c:392
#13 0x00005555557b29f5 in _start ()