* frame.c (has_stack_frames): Make public.

	* frame.c (has_stack_frames): Make public.
	(get_prev_frame): Don't allow a NULL this_frame anymore.
	* frame.h (has_stack_frames): Declare.
	* varobj.c (find_frame_addr_in_frame_chain): Don't ever pass NULL
	to get_prev_frame, instead start at get_current_frame.
	(varobj_create): Check has_stack_frames before getting any frame;
	eliminate one usage of deprecated_safe_get_selected_frame.