Throw error when setting value of AnimatedValue to undefined

Summary:
Changelog: [Internal] Throw error when setting Animated value to undefined.

Background:
ReadableNativeMap removes keys that have undefined values. Somewhere some animation is setting the value to be undefined.

Follow up: Find a way to warn generally that undefined values are being set for maps that become ReadableNativeMaps

Reviewed By: JoshuaGross

Differential Revision: D20169325

fbshipit-source-id: 404b727dc238703ebe5f71a0939340d5f1b3b211

Libraries/Animated/src/nodes/AnimatedValue.js

@@ -239,6 +239,10 @@ class AnimatedValue extends AnimatedWithChildren {
   }
 
   _updateValue(value: number, flush: boolean): void {
+    if (value === undefined) {
+      throw new Error('Attempting to set value to undefined');
+    }
+
     this._value = value;
     if (flush) {
       _flush(this);