Throw helpful error if no default device is found

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>sh.ball</groupId>
     <artifactId>osci-render</artifactId>
-    <version>1.7.1</version>
+    <version>1.7.2</version>
 
     <name>osci-render</name>
 

src/main/java/sh/ball/gui/Controller.java

@@ -133,6 +133,9 @@ public class Controller implements Initializable, FrequencyListener, Listener {
     frames.addListener(this);
     this.producer = new FrameProducer<>(audioPlayer, frames);
     this.defaultDevice = audioPlayer.getDefaultDevice();
+    if (defaultDevice == null) {
+      throw new RuntimeException("No default audio device found!");
+    }
     this.sampleRate = defaultDevice.sampleRate();
     this.rotateEffect = new RotateEffect(sampleRate);
     this.translateEffect = new TranslateEffect(sampleRate);