* Throw exception if the spot light computed cosine angle is not valid

jme3-core/src/main/java/com/jme3/light/SpotLight.java

@@ -77,6 +77,10 @@ public class SpotLight extends Light implements Savable {
             outerCos -= 0.001f;
         }
         packedAngleCos += outerCos;
+
+        if (packedAngleCos == 0.0f) {
+            throw new IllegalArgumentException("Packed angle cosine is invalid");
+        }
     }
 
     @Override