Qt: Fix a crash in the memory viewer

CHANGES

@@ -6,6 +6,7 @@ Bugfixes:
  - Qt: Fix clear button/analog buttons in gamepad mapper on some platforms
  - GBA Video: Fix _mix for 15-bit color
  - Qt: Fix font size in memory viewer
+ - Qt: Fix a crash in the memory viewer
 Misc:
  - GBA Audio: Implement missing flags on SOUNDCNT_X register
 

src/platform/qt/MemoryView.cpp

@@ -80,6 +80,9 @@ void MemoryView::updateStatus() {
 		m_ui.uintVal->clear();
 		return;
 	}
+	if (!m_controller->isLoaded()) {
+		return;
+	}
 	ARMCore* cpu = m_controller->thread()->cpu;
 	union {
 		uint32_t u32;