Tests for null if no remote address.

fixes gh-430

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/headers/XForwardedHeadersFilter.java

@@ -172,7 +172,9 @@ public class XForwardedHeadersFilter implements HttpHeadersFilter, Ordered {
 		original.entrySet().stream()
 				.forEach(entry -> updated.addAll(entry.getKey(), entry.getValue()));
 
-		if (isForEnabled()) {
+		if (isForEnabled() &&
+			request.getRemoteAddress() != null && request.getRemoteAddress().getAddress() != null)
+		{
 			String remoteAddr = request.getRemoteAddress().getAddress().getHostAddress();
 			List<String> xforwarded = original.get(X_FORWARDED_FOR_HEADER);
 			// prevent duplicates

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/headers/XForwardedHeadersFilterTests.java

@@ -37,6 +37,25 @@ import static org.springframework.cloud.gateway.filter.headers.XForwardedHeaders
  */
 public class XForwardedHeadersFilterTests {
 
+	@Test
+	public void remoteAddressIsNull() throws Exception {
+		MockServerHttpRequest request = MockServerHttpRequest
+				.get("http://localhost:8080/get")
+				.header(HttpHeaders.HOST, "myhost")
+				.build();
+
+		XForwardedHeadersFilter filter = new XForwardedHeadersFilter();
+
+		HttpHeaders headers = filter.filter(request.getHeaders(), MockServerWebExchange.from(request));
+
+		assertThat(headers).containsKeys(X_FORWARDED_HOST_HEADER,
+				X_FORWARDED_PORT_HEADER, X_FORWARDED_PROTO_HEADER);
+
+		assertThat(headers.getFirst(X_FORWARDED_HOST_HEADER)).isEqualTo("localhost:8080");
+		assertThat(headers.getFirst(X_FORWARDED_PORT_HEADER)).isEqualTo("8080");
+		assertThat(headers.getFirst(X_FORWARDED_PROTO_HEADER)).isEqualTo("http");
+	}
+
 	@Test
 	public void xForwardedHeadersDoNotExist() throws Exception {
 		MockServerHttpRequest request = MockServerHttpRequest