Reorder command line arguments check and registry operations.

When openvpn is not installed, HKLM\Software\OpenVPN registry is missing,
however, it should not fail on running "openvpn-gui.exe --help". Such
usage might be useful for smoke testing, for example (build openvpn-gui.exe
on AppVeyor, run it, check whether window is shown or not)

main.c

@@ -174,12 +174,12 @@ int WINAPI _tWinMain (HINSTANCE hThisInstance,
         exit(1);
     }
 
-  UpdateRegistry(); /* Checks version change and update keys/values */
-
-  GetRegistryKeys();
   /* Parse command-line options */
   ProcessCommandLine(&o, GetCommandLine());
 
+  UpdateRegistry(); /* Checks version change and update keys/values */
+  GetRegistryKeys();
+
   EnsureDirExists(o.config_dir);
 
   if (!CheckVersion()) {