FIX:fixed sending print failure due to long plate name

Change-Id: I89f32f7d7f214d55051e736f834e0e49d7c808ab

src/slic3r/GUI/Jobs/PrintJob.cpp

@@ -70,9 +70,11 @@ std::string PrintJob::truncate_string(const std::string& str, size_t maxLength)
         return str;
     }
 
-    std::string truncatedStr = str.substr(0, maxLength - 3);
+    wxString local_str = wxString::FromUTF8(str);
+    wxString truncatedStr = local_str.Mid(0, maxLength - 3);
     truncatedStr.append("...");
-    return truncatedStr;
+
+    return truncatedStr.utf8_string();
 }