added wxSafeConvertMB2WX/WX2MB() and use them when interfacing with C functions which crash if we pass them NULL pointers

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@44771 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/strconv.cpp

@@ -3650,9 +3650,39 @@ WXDLLIMPEXP_DATA_BASE(wxMBConv *) wxConvFileName = &
 #else
                                     wxConvUTF8Obj;
 #endif
-#else
+#else // !__WXOSX__
                                     wxConvLibcObj;
-#endif
+#endif // __WXOSX__/!__WXOSX__
+
+#if wxUSE_UNICODE
+
+wxWCharBuffer wxSafeConvertMB2WX(const char *s)
+{
+    if ( !s )
+        return wxWCharBuffer();
+
+    wxWCharBuffer wbuf(wxConvLibc.cMB2WX(s));
+    if ( !wbuf )
+        wbuf = wxConvUTF8.cMB2WX(s);
+    if ( !wbuf )
+        wbuf = wxConvISO8859_1.cMB2WX(s);
+
+    return wbuf;
+}
+
+wxCharBuffer wxSafeConvertWX2MB(const wchar_t *ws)
+{
+    if ( !ws )
+        return wxCharBuffer();
+
+    wxCharBuffer buf(wxConvLibc.cWX2MB(ws));
+    if ( !buf )
+        buf = wxMBConvUTF8(wxMBConvUTF8::MAP_INVALID_UTF8_TO_OCTAL).cWX2MB(ws);
+
+    return buf;
+}
+
+#endif // wxUSE_UNICODE
 
 #else // !wxUSE_WCHAR_T