Reset the contentDescription when accessibility text is empty to revoke stale state

Summary:
This diff fixes accessibility value setter in BaseViewManager.java when the accessibility value is null. This is needed when we reset the value and would like to make sure the content description reflects the expected state, instead of the stale state when the value is set last time.

Changelog:
[Android][Fixed] - Reset accessibility value when it gets a null value

Reviewed By: NickGerleman

Differential Revision: D42160904

fbshipit-source-id: a8115a268461c8340d38350ab6fd3f21e4b14959

Author: Xin Chen

ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java

@@ -366,12 +366,13 @@ public void setAccessibilityActions(T view, ReadableArray accessibilityActions)
   @ReactProp(name = ViewProps.ACCESSIBILITY_VALUE)
   public void setAccessibilityValue(T view, ReadableMap accessibilityValue) {
     if (accessibilityValue == null) {
-      return;
-    }
-
-    view.setTag(R.id.accessibility_value, accessibilityValue);
-    if (accessibilityValue.hasKey("text")) {
-      updateViewContentDescription(view);
+      view.setTag(R.id.accessibility_value, null);
+      view.setContentDescription(null);
+    } else {
+      view.setTag(R.id.accessibility_value, accessibilityValue);
+      if (accessibilityValue.hasKey("text")) {
+        updateViewContentDescription(view);
+      }
     }
   }