"bash: : command not found" in System Tool - XDG menu items

[Gandalf73]

Hello,
I discovered a little strange behaviour into the Cygwin Portable application.
I try to explain it.
When I run "startxwin" from a previous open bash prompt and I use the "system tools" items from XDG menu,
(on TrayMenu items), I see the corresponding behaviour (i.e. I can see a new window with bash prompt of Mintty or UxTerm or XTerm with prompt sign '$')
On the other hand,
when I start X server with Cygwin menu (throughout "X Server" item) and after I run Xterm, Uxterm or Cygwin Terminal (mintty) (always throughout "System Tools" Menu item) ,
I can observe the terminal correct launched on own window but on the top of the prompt it appears "bash: : command not found "
So I think it can be into the batches files script a "false/spurious character" (it seems a space).
Unfortunately I am not able to check into the source.
I hope that my discovery is useful
Thanks a lot again
Regards
A