Fixes #613

Author: skarpenko

feign-reactor-core/src/main/java/reactivefeign/methodhandler/PublisherClientMethodHandler.java

@@ -189,8 +189,12 @@ private String queryLine(Map<String, Collection<String>> queries) {
             Collection<String> valuesEncoded = query.getValue().stream()
                     .map(value -> UriUtils.encode(value, UTF_8))
                     .collect(toList());
-            queryBuilder.append('&');
-            queryBuilder.append(collectionFormat.join(query.getKey(), valuesEncoded, UTF_8));
+
+            CharSequence queryString = collectionFormat.join(query.getKey(), valuesEncoded, UTF_8);
+            if(queryString.length() > 0){
+                queryBuilder.append('&');
+                queryBuilder.append(queryString);
+            }
         }
         if(queryBuilder.length() > 0) {
             queryBuilder.deleteCharAt(0);

feign-reactor-core/src/test/java/reactivefeign/allfeatures/AllFeaturesTest.java

@@ -155,7 +155,7 @@ public void shouldPassEmptyParameterInUrl() {
 
 	@Test
 	public void shouldNotReturnNullPassedParametersNew() {
-		Map<String, String> paramMap = new HashMap<String, String>() {
+		Map<String, String> paramMap = new HashMap<>() {
 			{
 				put("paramKey", "paramValue");
 				put("paramKeyNull", null);

feign-reactor-spring-configuration/src/main/java/reactivefeign/spring/config/ReactiveFeignAutoConfiguration.java

@@ -41,7 +41,7 @@ public ReactiveFeignNamedContextFactory reactiveFeignContext() {
 
     @Configuration
     @ConditionalOnClass(WebReactiveFeign.class)
-    public class WebClientReactiveFeignClientPropertiesAutoConfiguration {
+    public static class WebClientReactiveFeignClientPropertiesAutoConfiguration {
 
         @Bean
         @ConditionalOnMissingBean
@@ -54,7 +54,7 @@ public ReactiveFeignClientsProperties<WebReactiveOptions.Builder> webClientReact
 
     @Configuration
     @ConditionalOnClass(Java11ReactiveFeign.class)
-    public class Java11ReactiveFeignClientPropertiesAutoConfiguration {
+    public static class Java11ReactiveFeignClientPropertiesAutoConfiguration {
 
         @Bean
         @ConditionalOnMissingBean
@@ -67,7 +67,7 @@ public ReactiveFeignClientsProperties<Java11ReactiveOptions.Builder> java11React
 
     @Configuration
     @ConditionalOnClass(JettyReactiveFeign.class)
-    public class JettyReactiveFeignClientPropertiesAutoConfiguration {
+    public static class JettyReactiveFeignClientPropertiesAutoConfiguration {
 
         @Bean
         @ConditionalOnMissingBean