Fix clang compilation error

sdrbase/dsp/wavfilerecord.cpp

@@ -29,7 +29,7 @@
 
 #include "wavfilerecord.h"
 
-WavFileRecord::WavFileRecord(quint32 sampleRate=0, quint64 centerFrequency=0) :
+WavFileRecord::WavFileRecord(quint32 sampleRate, quint64 centerFrequency) :
     FileRecordInterface(),
     m_fileBase("test"),
     m_sampleRate(sampleRate),

sdrbase/dsp/wavfilerecord.h

@@ -85,7 +85,7 @@ public:
     };
 #pragma pack(pop)
 
-    WavFileRecord(quint32 sampleRate, quint64 centerFrequency);
+    WavFileRecord(quint32 sampleRate=0, quint64 centerFrequency=0);
     WavFileRecord(const QString& fileBase);
     virtual ~WavFileRecord();