fix: 'in' clause case for ORACLE (typeorm#5345)

* fixing 'in' clause case for ORACLE

* fix == to ===

Co-authored-by: Gerwin Brunner <gerwin.brunner@vilango.com>

src/find-options/FindOperator.ts

@@ -1,5 +1,6 @@
 import {FindOperatorType} from "./FindOperatorType";
 import {Connection} from "../";
+import {OracleDriver} from "../driver/oracle/OracleDriver";
 
 /**
  * Find Operator used in Find Conditions.
@@ -107,6 +108,9 @@ export class FindOperator<T> {
             case "between":
                 return `${aliasPath} BETWEEN ${parameters[0]} AND ${parameters[1]}`;
             case "in":
+                if (connection.driver instanceof OracleDriver && parameters.length === 0) {
+                    return `${aliasPath} IN (null)`;
+                }                
                 return `${aliasPath} IN (${parameters.join(", ")})`;
             case "any":
                 return `${aliasPath} = ANY(${parameters[0]})`;