==6002== Conditional jump or move depends on uninitialised value(s)
    ==6002==    at 0x8AD243A: KisSignalCompressor::start() (kis_signal_compressor.cpp:49)
    ==6002==    by 0x505DCEA: KisCanvas2::updateCanvas() (kis_canvas2.cpp:636)
    ==6002==    by 0x505E667: KisCanvas2::setCanvasWidget(QWidget*) (kis_canvas2.cpp:231)
    ==6002==    by 0x505FC98: KisCanvas2::createOpenGLCanvas() (kis_canvas2.cpp:413)
    ==6002==    by 0x5062147: KisCanvas2::createCanvas(bool) (kis_canvas2.cpp:439)
    ==6002==    by 0x50623DD: KisCanvas2::setup() (kis_canvas2.cpp:157)
    ==6002==    by 0x537453B: KisView::KisView(KisDocument*, KoCanvasResourceManager*, KActionCollection*, QWidget*) (KisView.cpp:229)
    ==6002==    by 0x536130C: KisPart::createView(KisDocument*, KoCanvasResourceManager*, KActionCollection*, QWidget*) (KisPart.cpp:258)
    ==6002==    by 0x5344A53: KisMainWindow::addViewAndNotifyLoadingCompleted(KisDocument*) (KisMainWindow.cpp:783)
    ==6002==    by 0x5344AAA: KisMainWindow::slotLoadCompleted() (KisMainWindow.cpp:810)
    ==6002==    by 0x5356434: KisMainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (moc_KisMainWindow.cpp:338)
    ==6002==    by 0x6AF58D9: QMetaObject::activate(QObject*, int, int, void**) (in /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.5.1)

This adds an UNDEFINED value that's used in the constructor of
KisSignalCompressor and moves setting the actual mode to the
constuctor of KisCanvas2; there's no reason to actually wait
with setting those properties until KisCanvas2::setup is
called.