[fix] prevent findNodeHandle throwing on unmounted components

Fix #1097

packages/react-native-web/src/exports/findNodeHandle/index.js

@@ -8,4 +8,15 @@
  */
 
 import { findDOMNode } from 'react-dom';
-export default findDOMNode;
+
+const findNodeHandle = component => {
+  let node;
+
+  try {
+    node = findDOMNode(component);
+  } catch (e) {}
+
+  return node;
+};
+
+export default findNodeHandle;

packages/react-native-web/src/modules/NativeMethodsMixin/index.js

@@ -100,6 +100,7 @@ const NativeMethodsMixin = {
       return;
     }
     const node = findNodeHandle(this);
+    if (node) {
       // Next state is determined by comparison to existing state (in the DOM).
       // Existing state has already gone through i18n transform
       const domProps = createDOMProps(null, nativeProps, style =>
@@ -107,6 +108,7 @@ const NativeMethodsMixin = {
       );
       UIManager.updateView(node, domProps, this);
     }
+  }
 };
 
 export default NativeMethodsMixin;