Improve taking de-embedding measurements

- Automatically restart measurement even when the sweep was stopped
- Fix crash due to zeroed de-embedding reference impedance
- Fix crash due to not cleaned up dialog pointer with dangling connections
- Automatically excite the correct ports for the measurement

Software/PC_Application/LibreVNA-GUI/Traces/trace.cpp

@@ -37,6 +37,7 @@ Trace::Trace(QString name, QColor color, QString live)
       reference_impedance(50.0),
       domain(DataType::Frequency),
       deembeddingActive(false),
+      deembedded_reference_impedance(50.0),
       lastMath(nullptr)
 {
     settings.valid = false;