Initialize variable word in complete

Initialize variable word in complete

The complete function should set parameter word to the end of the
word to complete. However, completion_find_completion_word may fail,
leaving word uninitialized.

To make sure word is always set, initialize it to the completion point
which is the end of the line parameter.

gdb/Changelog

	PR cli/24587
	* completer.c (complete): Initialize variable word.