[webview support lib] handle null isomporphic objects

Bug: 865062
Change-Id: I8efb1817b1b2bf390189ed117c8773b6a0329ded
Reviewed-on: https://chromium-review.googlesource.com/1244798Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Commit-Queue: Tobias Sargeant <tobiasjs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594142}

android_webview/support_library/java/src/org/chromium/support_lib_glue/IsomorphicAdapter.java

@@ -18,6 +18,9 @@ abstract class IsomorphicAdapter implements IsomorphicObjectBoundaryInterface {
     @Override
     public Object getOrCreatePeer(Callable<Object> creationCallable) throws Exception {
         AwSupportLibIsomorphic peeredObject = getPeeredObject();
+        if (peeredObject == null) {
+            return null;
+        }
         Object peer = peeredObject.getSupportLibObject();
         if (peer == null) {
             peeredObject.setSupportLibObject(peer = creationCallable.call());