Fix issue 370

https://github.com/q2a/question2answer/issues/370

qa-include/db/recalc.php

@@ -392,7 +392,7 @@
 */
 	{
 		return qa_db_read_one_assoc(qa_db_query_sub(
-			'SELECT blobid, content, format FROM ^blobs WHERE blobid>=# AND content IS NOT NULL',
+			'SELECT blobid, content, format FROM ^blobs WHERE blobid>=# AND content IS NOT NULL LIMIT 1',
 			$startblobid
 		), true);
 	}
@@ -421,4 +421,4 @@
 
 /*
 	Omit PHP closing tag to help avoid accidental output
-*/
\ No newline at end of file
+*/