fixed npe that lead to the revert

Author: gaaclarke

shell/platform/android/BUILD.gn

@@ -487,6 +487,7 @@ action("robolectric_tests") {
     "test/io/flutter/embedding/engine/systemchannels/PlatformChannelTest.java",
     "test/io/flutter/embedding/engine/systemchannels/RestorationChannelTest.java",
     "test/io/flutter/external/FlutterLaunchTests.java",
+    "test/io/flutter/plugin/common/BinaryCodecTest.java",
     "test/io/flutter/plugin/common/StandardMessageCodecTest.java",
     "test/io/flutter/plugin/common/StandardMethodCodecTest.java",
     "test/io/flutter/plugin/editing/InputConnectionAdaptorTest.java",

shell/platform/android/io/flutter/plugin/common/BinaryCodec.java

@@ -4,6 +4,7 @@
 
 package io.flutter.plugin.common;
 
+import androidx.annotation.Nullable;
 import java.nio.ByteBuffer;
 
 /**
@@ -45,13 +46,15 @@ private BinaryCodec(boolean returnsDirectByteBufferFromDecoding) {
   }
 
   @Override
-  public ByteBuffer encodeMessage(ByteBuffer message) {
+  public ByteBuffer encodeMessage(@Nullable ByteBuffer message) {
     return message;
   }
 
   @Override
-  public ByteBuffer decodeMessage(ByteBuffer message) {
-    if (returnsDirectByteBufferFromDecoding) {
+  public ByteBuffer decodeMessage(@Nullable ByteBuffer message) {
+    if (message == null) {
+      return message;
+    } else if (returnsDirectByteBufferFromDecoding) {
       return message;
     } else {
       ByteBuffer result = ByteBuffer.allocate(message.capacity());

shell/platform/android/test/io/flutter/FlutterTestSuite.java

@@ -30,6 +30,7 @@
 import io.flutter.embedding.engine.systemchannels.PlatformChannelTest;
 import io.flutter.embedding.engine.systemchannels.RestorationChannelTest;
 import io.flutter.external.FlutterLaunchTests;
+import io.flutter.plugin.common.BinaryCodecTest;
 import io.flutter.plugin.common.StandardMessageCodecTest;
 import io.flutter.plugin.common.StandardMethodCodecTest;
 import io.flutter.plugin.editing.InputConnectionAdaptorTest;
@@ -53,6 +54,7 @@
   AccessibilityBridgeTest.class,
   AndroidKeyProcessorTest.class,
   ApplicationInfoLoaderTest.class,
+  BinaryCodecTest.class,
   DartExecutorTest.class,
   DartMessengerTest.class,
   FlutterActivityAndFragmentDelegateTest.class,

shell/platform/android/test/io/flutter/plugin/common/BinaryCodecTest.java

@@ -0,0 +1,17 @@
+package io.flutter.plugin.common;
+
+import static org.junit.Assert.assertNull;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+@Config(manifest = Config.NONE)
+@RunWith(RobolectricTestRunner.class)
+public class BinaryCodecTest {
+  @Test
+  public void decodeNull() {
+    assertNull(BinaryCodec.INSTANCE.decodeMessage(null));
+  }
+}