From 134c0204f3b947276c0e6f26f4fe426b5cba5c06 Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Sun, 5 Mar 2017 22:18:04 +0100
Subject: [PATCH] Do not return a negative background color

fixes #1429 and similar
---
 autoload/airline/highlighter.vim | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/autoload/airline/highlighter.vim b/autoload/airline/highlighter.vim
index 7178e6b4..af8e83dc 100644
--- a/autoload/airline/highlighter.vim
+++ b/autoload/airline/highlighter.vim
@@ -108,6 +108,10 @@ function! s:CheckDefined(colors)
   " but at least this makes sure, the group will be defined
   let fg = g:airline#highlighter#normal_fg_hi
   let bg = synIDattr(synIDtrans(hlID('Normal')), 'bg', 'cterm')
+  if bg < 0
+    " in case there is no background color defined for Normal
+    let bg = a:colors[3]
+  endif
   return a:colors[0:1] + [fg, bg] + [a:colors[4]]
 endfunction