Fix for concat expression seperator, it always returned a space and not the given argument seperator. Defaults back to a space if none are given in the arguments.

Author: stephan-cream

lib/internal/Magento/Framework/DB/Sql/ConcatExpression.php

@@ -65,7 +65,7 @@ public function __toString()
         }
         return sprintf(
             'TRIM(%s)',
-            $this->adapter->getConcatSql($columns, ' ')
+            $this->adapter->getConcatSql($columns, $this->seperator)
         );
     }
 }