Fix segmentation fault issue when using WX port command line

on Linux and MacOS.

src/wx/wxvbam.cpp

@@ -590,7 +590,8 @@ bool wxvbamApp::OnCmdLineParsed(wxCmdLineParser& cl)
 }
 
 wxvbamApp::~wxvbamApp() {
-    free(home);
+    if (home != NULL)
+	free(home);
 }
 
 MainFrame::MainFrame()

src/wx/wxvbam.h

@@ -142,7 +142,7 @@ protected:
 
 private:
     wxPathList config_path;
-    char* home;
+    char* home = NULL;
 };
 
 DECLARE_APP(wxvbamApp);