Fixed some compilation issues

plugins/samplemimo/testmi/testmiplugin.cpp

@@ -64,7 +64,7 @@ void TestMIPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevices& or
     originDevices.append(OriginDevice(
         "TestMI",         // Displayable name
         m_hardwareID,     // Hardware ID
-        QString::null,    // Serial
+        QString(),        // Serial
         0,                // Sequence
         2,                // Number of Rx streams
         0                 // Number of Tx streams

plugins/samplesink/filesink/filesinkplugin.cpp

@@ -63,7 +63,7 @@ void FileSinkPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevices&
     originDevices.append(OriginDevice(
         "FileSink",
         m_hardwareID,
-        QString::null,
+        QString(),
         0, // Sequence
         0, // nb Rx
         1  // nb Tx

plugins/samplesink/localoutput/localoutputplugin.cpp

@@ -64,7 +64,7 @@ void LocalOutputPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevice
     originDevices.append(OriginDevice(
         "LocalOutput",
         m_hardwareID,
-        QString::null,
+        QString(),
         0, // Sequence
         0, // nb Rx
         1  // nb Tx

plugins/samplesink/remoteoutput/remoteoutputplugin.cpp

@@ -64,7 +64,7 @@ void RemoteOutputPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevic
     originDevices.append(OriginDevice(
         "RemoteOutput",
         m_hardwareID,
-        QString::null,
+        QString(),
         0, // Sequence
         0, // nb Rx
         1  // nb Tx

plugins/samplesource/fileinput/fileinputplugin.cpp

@@ -64,7 +64,7 @@ void FileInputPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevices&
     originDevices.append(OriginDevice(
         "FileInput",
         m_hardwareID,
-        QString::null,
+        QString(),
         0,
         1, // nb Rx
         0  // nb Tx

plugins/samplesource/kiwisdr/kiwisdrplugin.cpp

@@ -65,7 +65,7 @@ void KiwiSDRPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevices& o
     originDevices.append(OriginDevice(
         "KiwiSDR",
         m_hardwareID,
-        QString::null,
+        QString(),
         0,
         1, // nb Rx
         0  // nb Tx

plugins/samplesource/localinput/localinputplugin.cpp

@@ -64,7 +64,7 @@ void LocalInputPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevices
     originDevices.append(OriginDevice(
         "LocalInput",
         m_hardwareID,
-        QString::null,
+        QString(),
         0,
         1, // nb Rx
         0  // nb Tx

plugins/samplesource/remoteinput/remoteinputplugin.cpp

@@ -64,7 +64,7 @@ void RemoteInputPlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevice
     originDevices.append(OriginDevice(
         "RemoteInput",
         m_hardwareID,
-        QString::null,
+        QString(),
         0,
         1, // nb Rx
         0  // nb Tx

plugins/samplesource/testsource/testsourceplugin.cpp

@@ -64,7 +64,7 @@ void TestSourcePlugin::enumOriginDevices(QStringList& listedHwIds, OriginDevices
     originDevices.append(OriginDevice(
         "TestSource",
         m_hardwareID,
-        QString::null,
+        QString(),
         0,
         1, // nb Rx
         0  // nb Tx

sdrbase/dsp/dspdevicemimoengine.cpp

@@ -101,6 +101,8 @@ bool DSPDeviceMIMOEngine::initProcess(int subsystemIndex)
         DSPGenerationInit cmd;
         return m_syncMessenger.sendWait(cmd) == StReady;
     }
+
+    return false;
 }
 
 bool DSPDeviceMIMOEngine::startProcess(int subsystemIndex)
@@ -116,6 +118,8 @@ bool DSPDeviceMIMOEngine::startProcess(int subsystemIndex)
 	    DSPGenerationStart cmd;
 	    return m_syncMessenger.sendWait(cmd) == StRunning;
     }
+
+    return false;
 }
 
 void DSPDeviceMIMOEngine::stopProcess(int subsystemIndex)

sdrbase/util/simpleserializer.h

@@ -60,7 +60,7 @@ public:
 	bool readDouble(quint32 id, double* result, double def = 0) const;
 	bool readReal(quint32 id, Real* result, Real def = 0) const;
 	bool readBool(quint32 id, bool* result, bool def = false) const;
-	bool readString(quint32 id, QString* result, const QString& def = QString::null) const;
+	bool readString(quint32 id, QString* result, const QString& def = QString()) const;
 	bool readBlob(quint32 id, QByteArray* result, const QByteArray& def = QByteArray()) const;
 
 	bool isValid() const { return m_valid; }