Merge pull request square#2471 from yschimke/insecure_npe

fix NPE with okcurl insecure mode

okcurl/src/main/java/okhttp3/curl/Main.java

@@ -251,7 +251,7 @@ private static SSLSocketFactory createInsecureSslSocketFactory() {
         }
 
         @Override public X509Certificate[] getAcceptedIssuers() {
-          return null;
+          return new X509Certificate[0];
         }
       };
       context.init(null, new TrustManager[] {permissive}, null);