fix: add missing type for Qt slot

(cherry picked from commit ad139d67c2)

src/nexus.cpp

@@ -94,6 +94,7 @@ void Nexus::start()
     qRegisterMetaType<const int16_t*>("const int16_t*");
     qRegisterMetaType<int32_t>("int32_t");
     qRegisterMetaType<int64_t>("int64_t");
+    qRegisterMetaType<size_t>("size_t");
     qRegisterMetaType<QPixmap>("QPixmap");
     qRegisterMetaType<Profile*>("Profile*");
     qRegisterMetaType<ToxAV*>("ToxAV*");