Adds a check for an empty URI in updateToHttpsIfNeeded. Fixes #1690.

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/ribbon/RibbonUtils.java

@@ -71,7 +71,7 @@ public class RibbonUtils {
 	public static URI updateToHttpsIfNeeded(URI uri, IClientConfig config, ServerIntrospector serverIntrospector,
 			Server server) {
 		String scheme = uri.getScheme();
-		if (!"https".equals(scheme) && isSecure(config, serverIntrospector, server)) {
+		if (!"".equals(uri.toString()) && !"https".equals(scheme) && isSecure(config, serverIntrospector, server)) {
 			UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromUri(uri).scheme("https");
 			if (uri.getRawQuery() != null) {
 				// When building the URI, UriComponentsBuilder verify the allowed characters and does not 

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/ribbon/RibbonUtilsTests.java

@@ -110,6 +110,14 @@ public class RibbonUtilsTests {
 				"https://foo/%20bar?hello=1%202")));
 	}
 
+	@Test
+	public void emptyStringUri() throws URISyntaxException {
+		URI original = new URI("");
+		URI updated = updateToHttpsIfNeeded(original, SECURE_CONFIG, SECURE_INTROSPECTOR, SERVER);
+		Assert.assertThat("URI should be the emptry string", updated, is(new URI(
+				"")));
+	}
+
 	static DefaultClientConfigImpl getConfig(boolean value) {
 		DefaultClientConfigImpl config = new DefaultClientConfigImpl();
 		config.setProperty(CommonClientConfigKey.IsSecure, value);