[IntelliJ][RunConf]Save config without main class will pops error dialog

[jingyanjingyan]

Build: dev1007

Repro Steps:

1. Create a config file and leave the main class empty
2. Save

Result:
Pops dialog "Main Class Name should not be null"

Expect:
Should allow saving config without main class

[jingyanjingyan]

Fix in dev 1022