Make SetupServerArgs callable without NodeContext

bitcoin-gui code needs to call SetupServerArgs but will not have a
NodeContext object if it is communicating with an external bitcoin-node
process.

src/qt/bitcoin.cpp

@@ -490,7 +490,7 @@ int GuiMain(int argc, char* argv[])
 
     /// 2. Parse command-line options. We do this after qt in order to show an error if there are problems parsing these
     // Command-line options take precedence:
-    SetupServerArgs(node_context);
+    SetupServerArgs(gArgs);
     SetupUIArgs(gArgs);
     std::string error;
     if (!gArgs.ParseParameters(argc, argv, error)) {