Avoid crashing in Fabric/Paper interop without bridge [1/n]

Summary:
Fabric/Paper interop expects bridge to be contained in `contextContainer`, and crashes if it's not there.

This diff avoids a crash, and instead fails silently. Future diffs in stack will enable `RCTComponentData` and `RCTLegacyViewManagerInteropCoordinator` to function without the bridge.

Changelog: [Internal]

Reviewed By: fkgozali

Differential Revision: D27374809

fbshipit-source-id: 2c9e03a1eaf5bcaa57887b203221111015cf4de5

ReactCommon/react/renderer/components/legacyviewmanagerinterop/LegacyViewManagerInteropComponentDescriptor.mm

@@ -59,8 +59,13 @@ static std::shared_ptr<void> const constructCoordinator(
   auto moduleName = moduleNameFromComponentName(componentName);
   Class module = NSClassFromString(RCTNSStringFromString(moduleName));
   assert(module);
-  RCTBridge *bridge = (RCTBridge *)unwrapManagedObjectWeakly(contextContainer->at<std::shared_ptr<void>>("Bridge"));
-  RCTComponentData *componentData = [[RCTComponentData alloc] initWithManagerClass:module bridge:bridge];
+  auto optionalBridge = contextContainer->find<std::shared_ptr<void>>("Bridge");
+  RCTBridge *bridge;
+  if (optionalBridge) {
+    bridge = unwrapManagedObjectWeakly(optionalBridge.value());
+  }
+  RCTComponentData *componentData = [[RCTComponentData alloc] initWithManagerClass:module
+                                                                            bridge:bridge];
   return wrapManagedObject([[RCTLegacyViewManagerInteropCoordinator alloc] initWithComponentData:componentData
                                                                                           bridge:bridge]);
 }