Actually use the (first) shell we found that the user meets the requirements

As discovered and reported by Deuce and Nelgin

src/sbbs3/logon.cpp

@@ -196,6 +196,8 @@ bool sbbs_t::logon()
 					break;
 			if (i == cfg.total_shells)
 				useron.shell = 0;
+			else
+				useron.shell = i;
 		}
 	}