Added check for missing url

Author: chillaq

client/src/main/java/io/split/client/dtos/ProxyConfiguration.java

@@ -44,7 +44,7 @@ public ProxyConfiguration.Builder url(URL url) throws MalformedURLException {
             try {
                 _proxyHost = new HttpHost(url.getProtocol(), url.getHost(), url.getPort());
             } catch (Exception exc) {
-                throw new MalformedURLException("roxy configuration is ignored. The proxy `url` was not provided or is malformed");
+                throw new MalformedURLException("Proxy configuration is invalid. The proxy `url` is malformed");
             }
             return this;
         }
@@ -56,6 +56,9 @@ public ProxyConfiguration.Builder mtls(String p12File, String passKey) {
         }
 
         public ProxyConfiguration build() {
+            if (_proxyHost == null) {
+                throw new IllegalArgumentException("Proxy configuration is invalid. The proxy `url` was not provided");
+            }
             return new ProxyConfiguration(_proxyHost, _provider, _p12File, _passKey);
         }
     }

client/src/test/java/io/split/client/SplitClientConfigTest.java

@@ -333,6 +333,14 @@ public void cannotUseInvalidUrl() throws MalformedURLException {
                 .build();
     }
 
+    @Test(expected = IllegalArgumentException.class)
+    public void mustUseUrl() throws MalformedURLException {
+        SplitClientConfig.builder()
+                .proxyConfiguration(new ProxyConfiguration.Builder()
+                        .build())
+                .build();
+    }
+
     @Test(expected = IllegalArgumentException.class)
     public void mustUseP12FileWithProxyMtls() throws MalformedURLException {
         SplitClientConfig.builder()