Minor refactorings + fix for dbo mysqli related to previous commit

git-svn-id: https://svn.cakephp.org/repo/branches/1.2.x.x@8261 3807eeeb-6ff5-0310-8944-8be069107fe0

cake/libs/model/datasources/dbo/dbo_mysqli.php

@@ -204,19 +204,22 @@ function value($data, $column = null, $safe = false) {
 			return 'NULL';
 		}
 		if ($data === '' && $column !== 'integer' && $column !== 'float' && $column !== 'boolean') {
-			return  "''";
+			return "''";
 		}
 		if (empty($column)) {
 			$column = $this->introspectType($data);
 		}
 
 		switch ($column) {
 			case 'boolean':
-				$data = $this->boolean((bool)$data);
+				return $this->boolean((bool)$data);
 			break;
 			case 'integer' :
 			case 'float' :
 			case null :
+				if ($data === '') {
+					return 'NULL';
+				}
 				if ((is_int($data) || is_float($data) || $data === '0') || (
 					is_numeric($data) && strpos($data, ',') === false &&
 					$data[0] != '0' && strpos($data, 'e') === false)) {