Minor assignment fix.
Can not use $array[] for reading.
diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index 393a1cd..d0af66d 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -281,7 +281,7 @@
 					$v = trim($v);
 					$this->_track_aliases($v);
 
-					$v = $this->qb_from[] = $this->protect_identifiers($v, TRUE, NULL, FALSE);
+					$this->qb_from[] = $v = $this->protect_identifiers($v, TRUE, NULL, FALSE);
 
 					if ($this->qb_caching === TRUE)
 					{