Corrected pin string construction from JPasswordField contents

[resoli]

In the initial loop on the various JPasswordField in MainFrame.abbinaCie(), getPassword() do not return the 1 character string content of the field, but a char[]. Adding it to the in-construction pin string implicitly calls toString[] on the char[], which results in a textual representation of it, something like this: [C@27716f4.
Here we propose passing the String.valueOf() of the char[] to the in-construction pin string.

[M0Rf30]

thanks for your contribution