Merge pull request #1320 from MeFisto94/fix-lwjgl3-double-stop

Fixes #1319 - LWJGL2: start(true) should not freeze when context could not be initialized

jme3-lwjgl/src/main/java/com/jme3/system/lwjgl/LwjglAbstractDisplay.java

@@ -121,13 +121,15 @@ public abstract class LwjglAbstractDisplay extends LwjglContext implements Runna
             super.internalCreate();
         } catch (Exception ex) {
             try {
-                if (Display.isCreated())
+                if (Display.isCreated()) {
                     Display.destroy();
+                }
             } catch (Exception ex2){
                 logger.log(Level.WARNING, null, ex2);
             }
 
             listener.handleError("Failed to create display", ex);
+            createdLock.notifyAll(); // Release the lock, so start(true) doesn't deadlock.
             return false; // if we failed to create display, do not continue
         }