[source] include/toplevel.mk: fix defconfig when ~/.openwrt/defconfig exists

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/?p=source.git;a=commitdiff;h=5b728074160bb1db064737baf95945ae2e972549

commit 5b728074160bb1db064737baf95945ae2e972549
Author: John Crispin <john at phrozen.org>
AuthorDate: Mon Jul 4 11:08:58 2016 +0200

    include/toplevel.mk: fix defconfig when ~/.openwrt/defconfig exists
    
    ./scripts/feeds update will reset the .config file if ~/.openwrt/defconfig
    exists, thus resetting the target to ar71xx.
    
    Signed-off-by: John Crispin <john at phrozen.org>
---
 include/toplevel.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/toplevel.mk b/include/toplevel.mk
index 581083d..3844f3c 100644
--- a/include/toplevel.mk
+++ b/include/toplevel.mk
@@ -110,7 +110,7 @@ config-clean: FORCE
 
 defconfig: scripts/config/conf prepare-tmpinfo FORCE
 	touch .config
-	@if [ -e $(HOME)/.openwrt/defconfig ]; then cp $(HOME)/.openwrt/defconfig .config; fi
+	@if [  -s .config -a -e $(HOME)/.openwrt/defconfig ]; then cp $(HOME)/.openwrt/defconfig .config; fi
 	$< --defconfig=.config Config.in
 
 confdefault-y=allyes