unlock incompletely loaded cache

src/http/ngx_http_file_cache.c

diff --git a/src/http/ngx_http_file_cache.c b/src/http/ngx_http_file_cache.c
index 208752b..27ac441 100644
--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c
@@ -1103,6 +1103,7 @@
     cache->files = 0;
 
     if (ngx_walk_tree(&tree, &cache->path->name) == NGX_ABORT) {
+        cache->sh->loading = 0;
         return;
     }