refactor: use std::string for thread names

src/qt/guiutil.cpp

@@ -982,7 +982,7 @@ void PrintSlotException(
     std::string description = sender->metaObject()->className();
     description += "->";
     description += receiver->metaObject()->className();
-    PrintExceptionContinue(exception, description.c_str());
+    PrintExceptionContinue(exception, description);
 }
 
 void ShowModalDialogAsynchronously(QDialog* dialog)