Camera: fix broken CameraDevice listener on Mac that would trigger only once always.

modules/juce_video/native/juce_mac_CameraDevice.h

@@ -177,6 +177,9 @@ struct CameraDevice::Pimpl
     {
         const ScopedLock sl (listenerLock);
         listeners.call ([=] (Listener& l) { l.imageReceived (image); });
+
+        if (! listeners.isEmpty())
+            triggerImageCapture();
     }
 
     void triggerImageCapture()