fix fatal error that API is already in use

plugins/ImageGraph/Controller.php

@@ -12,7 +12,7 @@ namespace Piwik\Plugins\ImageGraph;
 
 use Piwik\Common;
 use Piwik\Piwik;
-use Piwik\Plugins\API\API;
+use Piwik\Plugins\API\API as APIPlugins;
 use Piwik\SettingsPiwik;
 use Piwik\View;
 
@@ -26,7 +26,7 @@ class Controller extends \Piwik\Controller
         $period = Common::getRequestVar('period', 'day', 'string');
         $date = Common::getRequestVar('date', 'today', 'string');
         $_GET['token_auth'] = Piwik::getCurrentUserTokenAuth();
-        $reports = API::getInstance()->getReportMetadata($idSite, $period, $date);
+        $reports = APIPlugins::getInstance()->getReportMetadata($idSite, $period, $date);
         $plot = array();
         foreach ($reports as $report) {
             if (!empty($report['imageGraphUrl'])) {
@@ -55,7 +55,7 @@ class Controller extends \Piwik\Controller
         $date = Common::getRequestVar('date', 'today', 'string');
 
         $_GET['token_auth'] = Piwik::getCurrentUserTokenAuth();
-        $availableReports = API::getInstance()->getReportMetadata($this->idSite, $period, $date);
+        $availableReports = APIPlugins::getInstance()->getReportMetadata($this->idSite, $period, $date);
         $view->availableReports = $availableReports;
         $view->graphTypes = array(
             '', // default graph type