#2055 MultiFrequencyTunerChannelSource Null Pointer Error On Channel Source Shutdown - different solution to resolve possible memory leak with previous solution. Also fixes P25 issue where a traffic channel that doesn't get started is returned to the traffic channel pool. (#2070)

Co-authored-by: Dennis Sheirer <dsheirer@github.com>

src/main/java/io/github/dsheirer/dsp/filter/channelizer/PolyphaseChannelManager.java

@@ -252,11 +252,16 @@ public class PolyphaseChannelManager implements ISourceEventProcessor
         synchronized(mBufferDispatcher)
         {
             mChannelSources.remove(channelSource);
-            mPolyphaseChannelizer.removeChannel(channelSource);
+
+            if(mPolyphaseChannelizer != null)
+            {
+                mPolyphaseChannelizer.removeChannel(channelSource);
+            }
+
             mSourceEventBroadcaster.broadcast(SourceEvent.channelCountChange(getTunerChannelCount()));
 
             //If this is the last/only channel, deregister to stop the sample buffers
-            if(mPolyphaseChannelizer.getRegisteredChannelCount() == 0)
+            if(mPolyphaseChannelizer != null && mPolyphaseChannelizer.getRegisteredChannelCount() == 0)
             {
                 mNativeBufferProvider.removeBufferListener(mBufferDispatcher);
                 mBufferDispatcher.stop();

src/main/java/io/github/dsheirer/module/decode/p25/P25TrafficChannelManager.java

@@ -1086,6 +1086,18 @@ public class P25TrafficChannelManager extends TrafficChannelManager implements I
             startChannelRequest.addPreloadDataContent(new P25FrequencyBandPreloadDataContent(mFrequencyBandMap.values()));
             getInterModuleEventBus().post(startChannelRequest);
         }
+        else
+        {
+            //Return the channel to the traffic channel pool since we didn't start it.
+            if(mManagedPhase1TrafficChannels.contains(trafficChannel))
+            {
+                mAvailablePhase1TrafficChannelQueue.add(trafficChannel);
+            }
+            else if(mManagedPhase2TrafficChannels.contains(trafficChannel))
+            {
+                mAvailablePhase2TrafficChannelQueue.add(trafficChannel);
+            }
+        }
     }
 
     /**

src/main/java/io/github/dsheirer/source/tuner/channel/MultiFrequencyTunerChannelSource.java

@@ -153,19 +153,13 @@ public class MultiFrequencyTunerChannelSource extends TunerChannelSource
     @Override
     public void stop()
     {
-        //Don't perform stop sequence if we haven't been started.  There can be a small window on startup where the
-        //channel rotation monitor can get ahead of the channel source and cause it to try to stop and rotate before
-        //it has even started, causing an error in the polyphase channel source.
-        if(mStarted)
-        {
-            mStarted = false;
+        mStarted = false;
 
-            if(mTunerChannelSource != null)
-            {
-                mTunerChannelSource.stop();
-                mTunerChannelSource.removeSourceEventListener();
-                mTunerChannelSource = null;
-            }
+        if(mTunerChannelSource != null)
+        {
+            mTunerChannelSource.stop();
+            mTunerChannelSource.removeSourceEventListener();
+            mTunerChannelSource = null;
         }
     }