Ensure Referrers.get does return an empty result if there aren't any archives (#15846)

* Ensure Referrers.get does return an empty result if there aren't any archives

* update expected test files

1 files changed, 6 insertions, 3 deletions

diff --git a/plugins/Referrers/API.php b/plugins/Referrers/API.php
index 38a74b2ada..8bc75044f8 100644
--- a/plugins/Referrers/API.php
+++ b/plugins/Referrers/API.php
@@ -18,7 +18,6 @@ use Piwik\DataTable\Filter\ColumnCallbackAddColumnPercentage;
 use Piwik\Date;
 use Piwik\Metrics;
 use Piwik\Piwik;
-use Piwik\Plugins\LocalDevUtilities\LocalDevUtilities;
 use Piwik\Plugins\Referrers\DataTable\Filter\GroupDifferentSocialWritings;
 use Piwik\Site;
 
@@ -753,8 +752,12 @@ class API extends \Piwik\Plugin\API
             $result = new DataTable\Map();
             $result->setKeyName($table->getKeyName());
             foreach ($table->getDataTables() as $label => $childTable) {
-                $referrerTypeTable = $this->createReferrerTypeTable($childTable);
-                $result->addTable($referrerTypeTable, $label);
+                if ($childTable->getRowsCount() > 0) {
+                    $referrerTypeTable = $this->createReferrerTypeTable($childTable);
+                    $result->addTable($referrerTypeTable, $label);
+                } else {
+                    $result->addTable(new DataTable(), $label);
+                }
             }
         } else {
             throw new \Exception("Unexpected DataTable type: " . get_class($table)); // sanity check