Fix windows leader conf (#1990)

* Fix windows leader conf
* Update following HEAD page
close #1973

autoload/SpaceVim/mapping/guide.vim

@@ -633,7 +633,7 @@ else
         \ 'g:_spacevim_mappings_space')
   call SpaceVim#plugins#help#regist_root({'SPC' : g:_spacevim_mappings_space})
 endif
-if !g:spacevim_vimcompatible
+if !g:spacevim_vimcompatible && !empty(g:spacevim_windows_leader)
   call SpaceVim#mapping#guide#register_prefix_descriptions(
         \ g:spacevim_windows_leader,
         \ 'g:_spacevim_mappings_windows')

autoload/SpaceVim/mapping/leader.vim

@@ -189,7 +189,7 @@ endfunction
 
 function! SpaceVim#mapping#leader#defindKEYs() abort
   let g:_spacevim_mappings_prefixs = {}
-  if !g:spacevim_vimcompatible
+  if !g:spacevim_vimcompatible && !empty(g:spacevim_windows_leader)
     let g:_spacevim_mappings_prefixs[g:spacevim_windows_leader] = {'name' : '+Window prefix'}
     call extend(g:_spacevim_mappings_prefixs[g:spacevim_windows_leader], g:_spacevim_mappings_windows)
   endif

wiki/en/Following-HEAD.md

@@ -43,6 +43,7 @@ The next release is v0.9.0.
 - Fix inactive windows statusline ([#1913](https://github.com/SpaceVim/SpaceVim/pull/1913))
 - Fix key binding `SPC f t` ([#1900](https://github.com/SpaceVim/SpaceVim/pull/1900))
 - Fix lsp support for haskell, javascript and typescript ([#1894](https://github.com/SpaceVim/SpaceVim/pull/1894))
+- can not set `windows_leader` to empty string ([#1990](https://github.com/SpaceVim/SpaceVim/pull/1990))
 
 ### Removed