Ignore blockingSendMessage calls after release.

Previously we'd end up blocking forever in this case, which
is the worst thing we could do :). We could either throw an
exception or just print a warning. Printing a warning is more
in line with what other methods do (Handler prints a "sending
message to dead thread" warning).

library/src/main/java/com/google/android/exoplayer/ExoPlayerImplInternal.java

@@ -158,6 +158,10 @@ import java.util.List;
 
 
   public synchronized void blockingSendMessage(ExoPlayerComponent target, int messageType,
   public synchronized void blockingSendMessage(ExoPlayerComponent target, int messageType,
       Object message) {
       Object message) {
+    if (released) {
+      Log.w(TAG, "Sent message(" + messageType + ") after release. Message ignored.");
+      return;
+    }
     int messageNumber = customMessagesSent++;
     int messageNumber = customMessagesSent++;
     handler.obtainMessage(MSG_CUSTOM, messageType, 0, Pair.create(target, message)).sendToTarget();
     handler.obtainMessage(MSG_CUSTOM, messageType, 0, Pair.create(target, message)).sendToTarget();
     while (customMessagesProcessed <= messageNumber) {
     while (customMessagesProcessed <= messageNumber) {
@@ -170,7 +174,9 @@ import java.util.List;
   }
   }
 
 
   public synchronized void release() {
   public synchronized void release() {
-    if (!released) {
+    if (released) {
+      return;
+    }
     handler.sendEmptyMessage(MSG_RELEASE);
     handler.sendEmptyMessage(MSG_RELEASE);
     while (!released) {
     while (!released) {
       try {
       try {
@@ -181,7 +187,6 @@ import java.util.List;
     }
     }
     internalPlaybackThread.quit();
     internalPlaybackThread.quit();
   }
   }
-  }
 
 
   @Override
   @Override
   public boolean handleMessage(Message msg) {
   public boolean handleMessage(Message msg) {