Fixed run on missing sample

src/signal_processor/soundsignalprocessor.py

@@ -39,6 +39,9 @@ class SoundSignalProcessor(AbcSignalProcessor):
         """
         soundsample_name = self.soundsensor.getvalue()
 
+        if not soundsample_name:  # No new sample... nothing to do
+            return
+
         try:
             sample_decision = self.soundpreprocessor.preprocesssignal(soundsample_name)
         except Exception as e: