only add client key if non-null

Author: Martin Zimmermann

Parse/src/main/java/com/parse/ParsePlugins.java

@@ -95,7 +95,6 @@ public ParseHttpResponse intercept(Chain chain) throws IOException {
             ParseHttpRequest request = chain.getRequest();
             ParseHttpRequest.Builder builder = new ParseHttpRequest.Builder(request)
                 .addHeader(ParseRESTCommand.HEADER_APPLICATION_ID, applicationId)
-                .addHeader(ParseRESTCommand.HEADER_CLIENT_KEY, clientKey)
                 .addHeader(ParseRESTCommand.HEADER_CLIENT_VERSION, Parse.externalVersionName())
                 .addHeader(
                     ParseRESTCommand.HEADER_APP_BUILD_VERSION,
@@ -112,6 +111,10 @@ public ParseHttpResponse intercept(Chain chain) throws IOException {
               // NETWORK_EXECUTOR
               builder.addHeader(ParseRESTCommand.HEADER_INSTALLATION_ID, installationId().get());
             }
+            // client key can be null with self-hosted Parse Server
+            if (clientKey != null) {
+              builder.addHeader(ParseRESTCommand.HEADER_CLIENT_KEY, clientKey);
+            }
             return chain.proceed(builder.build());
           }
         });