Fixed parsing of second in where if it is an Expression object.

Author: mikebronner

src/CacheKey.php

@@ -85,6 +85,10 @@ protected function getColumnClauses(array $where) : string
             $where["first"] = $this->expressionToString($where["first"]);
         }
 
+		if ($where["second"] instanceof Expression) {
+			$where["second"] = $this->expressionToString($where["second"]);
+		}
+        
         return "-{$where["boolean"]}_{$where["first"]}_{$where["operator"]}_{$where["second"]}";
     }