GLDebug: Throw an unchecked exception instead of returning null to enforce a crash when glGetError is not present.

jme3-core/src/main/java/com/jme3/renderer/opengl/GLDebug.java

@@ -134,9 +134,8 @@ public class GLDebug implements InvocationHandler {
                     new GLDebug(gl, obj)
             );
         } catch (NoSuchMethodException nsme) {
-            LOG.log(Level.SEVERE, "Could not initialize the proxy because the glGetError method wasn't found!",
+            throw new IllegalStateException("Could not initialize the proxy because the glGetError method wasn't found!",
                     nsme);
-            return null;
         }
     }
 }