Add missing null-checks.

android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java

Index: android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java b/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
index e0a7a946197f7756185b36df4349b565b7306db8..1746eb0fd520549faf3118a9b0bd330924caf1be 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
@@ -147,6 +147,8 @@ class AwWebContentsDelegateAdapter extends AwWebContentsDelegate {
         final Handler handler = new Handler(ThreadUtils.getUiThreadLooper()) {
             @Override
             public void handleMessage(Message msg) {
+                if (contentViewCore.getWebContents() == null) return;
+
                 switch(msg.what) {
                     case msgContinuePendingReload: {
                         contentViewCore.getWebContents().getNavigationController()