Upstream patch for YT-GD-538

Pulled from:
http://sourceforge.net/p/zbar/code/ci/825b6ec9244619cc616d592e657fc64b5d7b2c25/tree/zbar/jpeg.c?diff=0e183788061038ad5a32543e594ebe48bde89971

--- a/zbar/jpeg.c
+++ b/zbar/jpeg.c
@@ -79,8 +79,15 @@
 void skip_input_data (j_decompress_ptr cinfo,
                       long num_bytes)
 {
-    cinfo->src->next_input_byte = NULL;
-    cinfo->src->bytes_in_buffer = 0;
+    if(num_bytes > 0) {
+        if (num_bytes < cinfo->src->bytes_in_buffer) {
+            cinfo->src->next_input_byte += num_bytes;
+            cinfo->src->bytes_in_buffer -= num_bytes;
+        }
+        else {
+            fill_input_buffer(cinfo);
+        }
+    }
 }
 
 void term_source (j_decompress_ptr cinfo)