fix r2122:
*) update file buf pointers,
*) avoid "zero buf" alert

src/http/modules/ngx_http_range_filter_module.c

diff --git a/src/http/modules/ngx_http_range_filter_module.c b/src/http/modules/ngx_http_range_filter_module.c
index 377ca9b..4a15637 100644
--- a/src/http/modules/ngx_http_range_filter_module.c
+++ b/src/http/modules/ngx_http_range_filter_module.c
@@ -654,7 +654,13 @@
             ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                            "http range body skip");
 
+            if (buf->in_file) {
+                buf->file_pos = buf->file_last;
+            }
+
             buf->pos = buf->last;
+            buf->sync = 1;
+
             continue;
         }