test: fix NullPointerException in mock server (#2365)

* test: fix NullPointerException in mock server

Fix a potential NullPointerException in the mock server when a statement uses a
parameter of type ARRAY<BYTES> with a null element in the array.

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: olavloite

google-cloud-spanner/src/test/java/com/google/cloud/spanner/DatabaseClientImplTest.java

@@ -84,6 +84,7 @@
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Base64;
 import java.util.Collections;
 import java.util.List;
@@ -2950,7 +2951,7 @@ public void testStatementWithBytesArrayParameter() {
         Statement.newBuilder("select id from test where b=@p1")
             .bind("p1")
             .toBytesArray(
-                ImmutableList.of(ByteArray.copyFrom("test1"), ByteArray.copyFrom("test2")))
+                Arrays.asList(ByteArray.copyFrom("test1"), null, ByteArray.copyFrom("test2")))
             .build();
     mockSpanner.putStatementResult(StatementResult.query(statement, SELECT1_RESULTSET));
     DatabaseClient client =

google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java

@@ -1367,7 +1367,8 @@ private Statement buildStatement(
                             (Iterable<LazyByteArray>)
                                 GrpcStruct.decodeArrayValue(
                                     com.google.cloud.spanner.Type.bytes(), value.getListValue()),
-                            LazyByteArray::getByteArray));
+                            lazyByteArray ->
+                                lazyByteArray == null ? null : lazyByteArray.getByteArray()));
                 break;
               case DATE:
                 builder