[fix: vimui 'double free']
[fix: vimui 'double free']

	issue: connection timeout to vim causes double free
	reason: vimgdb::init() does not reset pointers to 0, hence if 'ui'
			is delete within 'cleanup()' those elements are freed again
	fix: set respective pointers to 0

jnow-87/vimgdb,jnow-87/vimgdb,jnow-87/vimgdb