keymap: fix missing keymap symbol, fix wrong condition

autoload/airline/extensions/keymap.vim

@@ -8,7 +8,7 @@ if !has('keymap')
 endif
 
 function! airline#extensions#keymap#status()
-  return printf('%s', (&keymap ? (g:airline_symbols.keymap . ' '. &keymap) : ''))
+  return printf('%s', (!empty(&keymap) ? (g:airline_symbols.keymap . ' '. &keymap) : ''))
 endfunction
 
 function! airline#extensions#keymap#init(ext)

autoload/airline/init.vim

@@ -69,7 +69,8 @@ function! airline#init#bootstrap()
           \ 'paste': 'PASTE',
           \ 'spell': 'SPELL',
           \ 'modified': '+',
-          \ 'space': ' '
+          \ 'space': ' ',
+          \ 'keymap': 'Keymap:'
           \  }, 'keep')
 
   if get(g:, 'airline_powerline_fonts', 0)