Use default 0 for nxt_info to avoid X to decimal conversion error in sim_io.py...

Use default 0 for nxt_info to avoid X to decimal conversion error in sim_io.py with tb_unb2c_test.vhd.

boards/uniboard2c/libraries/unb2c_board/src/vhdl/unb2c_board_system_info.vhd

@@ -57,7 +57,7 @@ ARCHITECTURE str OF unb2c_board_system_info IS
   
   SIGNAL hw_version_reg : STD_LOGIC_VECTOR(hw_version'RANGE);
   SIGNAL id_reg         : STD_LOGIC_VECTOR(id'RANGE);
-  SIGNAL nxt_info       : STD_LOGIC_VECTOR(info'RANGE);
+  SIGNAL nxt_info       : STD_LOGIC_VECTOR(info'RANGE) := (OTHERS=>'0');
 
   SIGNAL nxt_bck_id     : STD_LOGIC_VECTOR(bck_id'RANGE);
   SIGNAL nxt_chip_id    : STD_LOGIC_VECTOR(chip_id'RANGE);