Fix NPE in BQ's StandardTableDefinition

google-cloud-clients/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/StandardTableDefinition.java

@@ -57,12 +57,12 @@ public static class StreamingBuffer implements Serializable {
     }
 
     /** Returns a lower-bound estimate of the number of rows currently in the streaming buffer. */
-    public long getEstimatedRows() {
+    public Long getEstimatedRows() {
       return estimatedRows;
     }
 
     /** Returns a lower-bound estimate of the number of bytes currently in the streaming buffer. */
-    public long getEstimatedBytes() {
+    public Long getEstimatedBytes() {
       return estimatedBytes;
     }
 
@@ -95,10 +95,17 @@ public boolean equals(Object obj) {
     }
 
     Streamingbuffer toPb() {
-      return new Streamingbuffer()
-          .setEstimatedBytes(BigInteger.valueOf(estimatedBytes))
-          .setEstimatedRows(BigInteger.valueOf(estimatedRows))
-          .setOldestEntryTime(BigInteger.valueOf(oldestEntryTime));
+      Streamingbuffer buffer = new Streamingbuffer();
+      if (estimatedBytes != null) {
+        buffer.setEstimatedBytes(BigInteger.valueOf(estimatedBytes));
+      }
+      if (estimatedRows != null) {
+        buffer.setEstimatedRows(BigInteger.valueOf(estimatedRows));
+      }
+      if (oldestEntryTime != null) {
+        buffer.setOldestEntryTime(BigInteger.valueOf(oldestEntryTime));
+      }
+      return buffer;
     }
 
     static StreamingBuffer fromPb(Streamingbuffer streamingBufferPb) {

google-cloud-clients/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/StandardTableDefinitionTest.java

@@ -120,6 +120,11 @@ public void testFromPbWithNullEstimatedRowsAndBytes() {
         TABLE_DEFINITION.toPb().setStreamingBuffer(new Streamingbuffer()));
   }
 
+  @Test
+  public void testStreamingBufferWithNullFieldsToPb() {
+    new StreamingBuffer(null, null, null).toPb();
+  }
+
   private void compareStandardTableDefinition(
       StandardTableDefinition expected, StandardTableDefinition value) {
     assertEquals(expected, value);