SUMMARY
When using plasma-dialer when using version 1.3 (compiled from master) of the library on the Pinephone, this library causes a segmentation fault. Running under LLDB shows the issue is with Card::sources, specifically the issue is that IndexedPulseObject::d points to invalid memory:

* thread #1, name = 'plasmaphonedial', stop reason = signal SIGSEGV: invalid address (fault address: 0x18)
    frame #0: 0x0000fffff78fb948 libKF5PulseAudioQt.so.3`PulseAudioQt::Card::sources(this=0x0000000000000000) const at card.cpp:155:56
   152 
   153      const auto allSources = Context::instance()->sources();
   154      for (Source *source : allSources) {
-> 155          if (source->cardIndex() == IndexedPulseObject::d->m_index) {
   156              ret << source;
   157          }
   158      }

STEPS TO REPRODUCE
1. Make a call in plasma-dialer

OBSERVED RESULT
It crashes.

EXPECTED RESULT
It does not crash.

SOFTWARE/OS VERSIONS
Running Manjaro-ARM
plasma-dialer and pulseaudio-qt are compiled from source (on master branch)
KDE Plasma 5.21.5
Frameworks 5.82.0
Qt 5.15.2
Kernel 5.12.2-2-MANJARO-ARM