Check if instance is valid before calling C++

Summary:
Changelog: [internal]

Why does the crash happen?
We call method on invalid address. We crash on `std::weak_ptr::lock` because that's the first accessed ivar.
In D29020768 (https://github.com/facebook/react-native/commit/25e8fbe8ffa1c91522e91819a781434093f8b759), eventEmitter may be destroyed before an event is dispatched. Calling destroy on hybrid object destroys only C++ part.

Reviewed By: JoshuaGross

Differential Revision: D29194906

fbshipit-source-id: ae8d9d90aa8d98d69d29884e80d6b930b1e66870

ReactAndroid/src/main/java/com/facebook/react/fabric/events/EventEmitterWrapper.java

@@ -48,6 +48,9 @@ public class EventEmitterWrapper {
    * @param params {@link WritableMap} payload of the event
    */
   public void invoke(@NonNull String eventName, @Nullable WritableMap params) {
+    if (!isValid()) {
+      return;
+    }
     NativeMap payload = params == null ? new WritableNativeMap() : (NativeMap) params;
     invokeEvent(eventName, payload);
   }
@@ -61,6 +64,9 @@ public class EventEmitterWrapper {
    */
   public void invokeUnique(
       @NonNull String eventName, @Nullable WritableMap params, int customCoalesceKey) {
+    if (!isValid()) {
+      return;
+    }
     NativeMap payload = params == null ? new WritableNativeMap() : (NativeMap) params;
     invokeUniqueEvent(eventName, payload, customCoalesceKey);
   }
@@ -70,4 +76,11 @@ public class EventEmitterWrapper {
       mHybridData.resetNative();
     }
   }
+
+  private boolean isValid() {
+    if (mHybridData != null) {
+      return mHybridData.isValid();
+    }
+    return false;
+  }
 }