#1210 Resolves issue of tuner instances can't be garbage collected due to retained references. Updates several of the tuner controller and tuner editor classes to add/invoke dispose() methods to clear retained instance references. (#1216)

Co-authored-by: Denny Sheirer <sheirerd@ainfosec.com>

src/main/java/io/github/dsheirer/source/tuner/manager/ChannelSourceManager.java

@@ -36,6 +36,14 @@ public abstract class ChannelSourceManager implements ISourceEventProcessor
 {
     private Broadcaster<SourceEvent> mSourceEventBroadcaster = new Broadcaster<>();
 
+    /**
+     * Prepare for disposal
+     */
+    public void dispose()
+    {
+        mSourceEventBroadcaster.clear();
+    }
+
     /**
      * Sorted set of tuner channels being sourced by this source manager.  Set is ordered by frequency lowest to highest
      */

src/main/java/io/github/dsheirer/source/tuner/manager/FrequencyErrorCorrectionManager.java

@@ -49,6 +49,15 @@ public class FrequencyErrorCorrectionManager
         mTunerController = tunerController;
     }
 
+    /**
+     * Dispose of this manager instance and nullify references.
+     */
+    public void dispose()
+    {
+        setEnabled(false);
+        mTunerController = null;
+    }
+
     /**
      * Enables or disables automatic frequency PPM correction.
      * @param enabled to true to turn on automatic PPM adjustments.
@@ -80,7 +89,7 @@ public class FrequencyErrorCorrectionManager
      */
     private void applyCorrection()
     {
-        if(mEnabled && mTunerController.hasMeasuredFrequencyError())
+        if(mEnabled && mTunerController != null && mTunerController.hasMeasuredFrequencyError())
         {
             double frequencyCorrection = mTunerController.getFrequencyCorrection();
             frequencyCorrection -= mTunerController.getPPMFrequencyError();