fix up some warnings;

src/monitor/NodeStatusWnd.h

@@ -215,8 +215,6 @@ private:
         if (FVTerm::getFOutput()->getMaxColor() < 16)
             setBold();
 
-        const auto& wc = getColorTheme();
-
         if (!m_tx) {
             if (m_failed) {
                 setColor(FColor::Black, FColor::LightRed);

src/sysview/DynRegroupSubscriberWnd.h

@@ -169,7 +169,7 @@ private:
                 redraw();
             });
             m_subscriber.addCallback("changed", [&]() { 
-                if (m_subscriber.getText().c_str() == "") {
+                if (m_subscriber.getText().getLength() == 0U) {
                     m_srcId = 1U;
                     return;
                 }

src/sysview/NodeStatusWnd.h

@@ -283,8 +283,6 @@ private:
         if (FVTerm::getFOutput()->getMaxColor() < 16)
             setBold();
 
-        const auto& wc = getColorTheme();
-
         if (!m_tx) {
             if (m_failed) {
                 setColor(FColor::Black, FColor::LightRed);
@@ -732,8 +730,6 @@ private:
     {
         assert(wdgt != nullptr);
 
-        const auto& rootWidget = getRootWidget();
-
         uint8_t channelId = peerObj["channelId"].get<uint8_t>();
         uint32_t channelNo = peerObj["channelNo"].get<uint32_t>();