ensure correct linking of the socket manager initializer for static builds of wxWidgets

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58059 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/sockunix.cpp

@@ -107,6 +107,9 @@ wxSocketError wxSocketImplUnix::GetLastError() const
 void wxSocketImplUnix::DoEnableEvents(int flags, bool enable)
 {
     wxSocketManager * const manager = wxSocketManager::Get();
+    if (!manager)
+        return;
+
     if ( enable )
     {
         if ( flags & wxSOCKET_INPUT_FLAG )