Fix EmptyStackException (#2746)

android/app/src/main/java/com/reactnativenavigation/views/SnackbarAndFabContainer.java

 import com.reactnativenavigation.layouts.Layout;
 import com.reactnativenavigation.params.FabParams;
 import com.reactnativenavigation.params.SnackbarParams;
+import com.reactnativenavigation.screens.Screen;
+
+import java.util.EmptyStackException;
 
 public class SnackbarAndFabContainer extends CoordinatorLayout implements Snakbar.OnDismissListener, Subscriber{
     private Snakbar snakbar;
             @Override
             public void run() {
                 if (fabParams != null) {
-                    if (layout.getCurrentScreen().getScreenInstanceId().equals(fabParams.screenInstanceId)) {
+                    Screen currentScreen = null;
+                    try {
+                        currentScreen = layout.getCurrentScreen();
+                    } catch(EmptyStackException exception) {
+                        currentScreen = null;
+                    }
+                    if (currentScreen != null && currentScreen.getScreenInstanceId().equals(fabParams.screenInstanceId)) {
                         fabCoordinator.add(fabParams);
                     }
                 }