Follow up fix to #878002: Support multiple sources per mapping target in FeedsDataProcessor.

plugins/FeedsDataProcessor.inc

@@ -235,7 +235,12 @@ class FeedsDataProcessor extends FeedsProcessor {
       }
     }
     else {
-      $target_item[$target_element] = $value;
+      if (is_array($target_item[$target_element]) && is_array($value)) {
+        $target_item[$target_element] = array_merge($target_item[$target_element], $value);
+      }
+      else {
+        $target_item[$target_element] = $value;
+      }
     }
   }