Fix warning "(vcom-1246) Range 1 to 0 is null" for Modelsim/Questa.

Author: tasgomes

vunit/vhdl/data_types/src/id_pkg.vhd

@@ -22,7 +22,8 @@ package id_pkg is
   end record;
   constant null_id : id_t := (p_data => null_ptr);
   type id_vec_t is array (integer range <>) of id_t;
-  constant null_id_vec : id_vec_t := (1 to 0 => null_id);
+  constant null_string : string := "";
+  constant null_id_vec : id_vec_t(null_string'range) := (others => null_id);
 
   -- root_id is a nameless and predefined ID that is the parent to
   -- all user created top-level IDs (no parent was specified at creation)

vunit/vhdl/logging/src/log_levels_pkg.vhd

@@ -32,7 +32,8 @@ package log_levels_pkg is
     custom_level8);
 
   type log_level_vec_t is array (natural range <>) of log_level_t;
-  constant null_vec : log_level_vec_t(1 to 0) := (others => info);
+  constant null_string : string := "";
+  constant null_vec : log_level_vec_t(null_string'range) := (others => info);
 
   subtype alert_log_level_t is log_level_t range warning to failure;
   subtype legal_log_level_t is log_level_t range log_level_t'succ(null_log_level) to log_level_t'high;