Fix segmentation fault issue when using WX port command line

on Linux and MacOS.

src/wx/wxvbam.cpp

@@ -590,6 +590,7 @@ bool wxvbamApp::OnCmdLineParsed(wxCmdLineParser& cl)
 }
 
 wxvbamApp::~wxvbamApp() {
+    if (home != NULL)
 	free(home);
 }
 

src/wx/wxvbam.h

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