fix(_comp_finalize): preserve existing values of the finalizer hooks

Author: akinomyoga

bash_completion

@@ -953,11 +953,11 @@ _comp_finalize__original_return_trap=
 
 # This associative array contains the finalizer commands with the key
 # being the name of the completed command.
-declare -gA BASH_COMPLETION_FINALIZE_CMD_HOOKS=()
+declare -gA BASH_COMPLETION_FINALIZE_CMD_HOOKS
 
 # This array contains the general finalizer commands that will be
 # executed for all the commands.
-BASH_COMPLETION_FINALIZE_HOOKS=()
+declare -ga BASH_COMPLETION_FINALIZE_HOOKS
 
 _comp_finalize()
 {