Return last output of the sound channel 3 even if it's disabled.

This fixes the buzzing in "3D pocket pool" #3.

Author: trekawek

core/src/main/java/eu/rekawek/coffeegb/core/sound/SoundMode3.java

@@ -122,6 +122,7 @@ public void start() {
 
     @Override
     public void trigger() {
+        i = 0;
         resetFreqDivider();
         triggered = !gbc;
         if (gbc) {
@@ -132,14 +133,10 @@ public void trigger() {
     @Override
     public int tick() {
         ticksSinceRead++;
-        if (!updateLength()) {
-            return 0;
+        if (!channelEnabled) {
+            return lastOutput;
         }
-        if (!dacEnabled) {
-            return 0;
-        }
-
-        if ((getNr0() & (1 << 7)) == 0) {
+        if (!updateLength()) {
             return 0;
         }