merge r3513 from branch 2.0 to trunk

bug 1043 fixed: avoid warning when merging chunks. This warning was preventing
the PwgError to work correctly and the error code was not transmitted.

git-svn-id: http://piwigo.org/svn/trunk@3514 68402e56-0260-453c-a942-63ccdbb3a9ee

include/ws_functions.inc.php

@@ -963,6 +963,8 @@ function merge_chunks($output_filepath, $original_sum, $type)
 
   ws_logfile('[merge_chunks] memory_get_usage before loading chunks: '.memory_get_usage());
 
+  $i = 0;
+  
   foreach ($chunks as $chunk)
   {
     $string = file_get_contents($chunk);