only start/stop the audio engine if its been initialized

simple things first.

after some debugging on audio "ducking"

it looks like we only start to kill audio after we initialize the audio engine. this first "fix" simply prevents us from initializing the audio engine if its not already been initialized. when going into the background/foreground.

other than this, we initialize the audio engine when you first play an audio clip in `void AudioEvent::play()`

this still leaves an issue lying around where after we have initialized the audio engine we will now "forever" duck audio when we go into the background/foreground. but at least you should be able to avoid this entirely if you never load a file with audio.

Diffs=
d4b3118e1 only start/stop the audio engine if its been initialized (#7335)

Co-authored-by: Maxwell Talbot <[email protected]>

.rive_head

@@ -1 +1 @@
-dde676085908d492af545660cbbb19ee0d10d91d
+d4b3118e1930e8e60565938a7c266d092a1ed940

Source/Renderer/rive_renderer_view.mm

@@ -24,12 +24,20 @@ @implementation RiveRendererView
 
 - (void)didEnterBackground:(NSNotification*)notification
 {
-    rive::AudioEngine::RuntimeEngine()->stop();
+    auto engine = rive::AudioEngine::RuntimeEngine(false);
+    if (engine != nil)
+    {
+        engine->stop();
+    }
 }
 
 - (void)didEnterForeground:(NSNotification*)notification
 {
-    rive::AudioEngine::RuntimeEngine()->start();
+    auto engine = rive::AudioEngine::RuntimeEngine(false);
+    if (engine != nil)
+    {
+        engine->start();
+    }
 }
 
 - (instancetype)initWithCoder:(NSCoder*)decoder