fix "first character of the attachment name was missing"

src/cpp/MainAttachment.cpp

@@ -349,7 +349,7 @@ MainAttachment::extractLinks (const string &extractedPlainKAZ) {
     string name;
 
     if (startName != string::npos) {
-      name = string (extractedPlainKAZ, startName+3, stopName - startName - 3);
+      name = string (extractedPlainKAZ, startName+2, stopName -startName-2);
       // skip [> \r\n\t]
       string::size_type nextPos = name.find_first_not_of ("[>< \t\r\n\"]");
       if (nextPos != string::npos)