fix crash when unable to convert from local to utf-8

ChangeLog

@@ -1,6 +1,8 @@
  (Format: Year/Month/Day)
 Changes for 1.0rc2:
 *06/06/25:
+   * Fix crash when unable to convert between local and utf-8 encodings (Simon)
+     FbTk/FbString.cc
    * Fix DetachClient key command so new window is visible (Mark)
      Window.cc
 *06/06/24:

src/FbTk/FbString.cc

@@ -130,6 +130,9 @@ std::string recode(iconv_t cd,
     if (in.empty()) 
         return "";
 
+    if (cd == ((iconv_t)(-1)))
+        return in; // can't convert
+
     size_t insize = in.size();
     size_t outsize = insize;
     char * out = (char *) malloc(outsize * sizeof(char)); // need realloc