Refs #3582, fix bug in last commit.

git-svn-id: http://dev.piwik.org/svn/trunk@7699 59fd770c-687e-43c8-a1e3-f5a4ff64c105

plugins/API/API.php

@@ -562,7 +562,11 @@ class Piwik_API_API
 			// if hide/show columns specified, hide/show metrics & docs
 			$availableReport['metrics'] = $this->hideShowMetrics($availableReport['metrics']);
 			$availableReport['processedMetrics'] = $this->hideShowMetrics($availableReport['processedMetrics']);
-			$availableReport['metricsDocumentation'] = $this->hideShowMetrics($availableReport['metricsDocumentation']);
+			if (isset($availableReport['metricsDocumentation']))
+			{
+				$availableReport['metricsDocumentation'] =
+					$this->hideShowMetrics($availableReport['metricsDocumentation']);
+			}
 		}
 		
 		// Some plugins need to add custom metrics after all plugins hooked in