update: prevent crash on scene reload

Author: doranteseduardo

android/sharedCode/src/main/java/com/viro/core/Renderer.java

@@ -90,7 +90,9 @@ public Renderer(ClassLoader appClassLoader, Context context,
     }
 
     public void drawFrame() {
-        nativeDrawFrame(mNativeRef);
+        if (mNativeRef != 0) {
+            nativeDrawFrame(mNativeRef);
+        }
     }
     public void setVRModeEnabled(boolean enabled) { nativeSetVRModeEnabled(mNativeRef, enabled); }
 

android/sharedCode/src/main/java/com/viro/core/ViroViewARCore.java

@@ -297,6 +297,11 @@ public void onSurfaceChanged(GL10 gl, int width, int height) {
             if (view == null || view.mSurfaceView == null) {
                 return;
             }
+            
+            if (view.mDestroyed || view.mNativeRenderer == null) {
+                return;
+            }
+            
             view.mNativeRenderer.onSurfaceChanged(view.mSurfaceView.getHolder().getSurface(), width, height);
 
             // Notify ARCore session that the view size changed so that the perspective matrix and
@@ -316,11 +321,25 @@ public void onDrawFrame(GL10 gl) {
             if (view == null) {
                 return;
             }
+            
+            // Check if the view has been destroyed or is being destroyed
+            if (view.mDestroyed) {
+                return;
+            }
 
-            for (int i = 0; i < view.mFrameListeners.size(); i++) {
-                view.mFrameListeners.get(i).onDrawFrame();
+            if (view.mFrameListeners != null) {
+                for (int i = 0; i < view.mFrameListeners.size(); i++) {
+                    view.mFrameListeners.get(i).onDrawFrame();
+                }
+            }
+            
+            // Only draw if renderer is valid, initialized, has a scene, and ARCore is installed
+            if (view.mNativeRenderer != null 
+                    && view.mRendererSurfaceInitialized.get() 
+                    && view.mCurrentScene != null
+                    && view.mARCoreInstalled.get()) {
+                view.mNativeRenderer.drawFrame();
             }
-            view.mNativeRenderer.drawFrame();
         }
     }