Name can be omiitted from ->dbforge->modify_column()'s 2nd param if you aren't changing the name.
diff --git a/system/database/DB_forge.php b/system/database/DB_forge.php
index f40eac8..ce505f4 100644
--- a/system/database/DB_forge.php
+++ b/system/database/DB_forge.php
@@ -333,6 +333,12 @@
foreach ($field as $k => $v)
{
+ // If no name provided, use the current name
+ if ( ! isset($field[$k]['name']))
+ {
+ $field[$k]['name'] = $k;
+ }
+
$this->add_field(array($k => $field[$k]));
if (count($this->fields) == 0)