Fixes backspace key in password editor.

--- ../orig/berusky-1.1/src/berusky_gui.cpp	2007-04-22 09:47:30.000000000 +0200
+++ src/berusky_gui.cpp	2007-11-08 10:52:24.000000000 +0100
@@ -248,7 +248,7 @@
         bool character = key_to_ascii(data,&ascii_char);
         int  len = strlen(password);
       
-        if(character) {
+        if(character && ascii_char >= ' ') {
           if(len < MAX_PASSWORD-2) {
             password[len] = ascii_char;
             password[len+1] = '\0';