ThemeServicePreAction Null Pointer Exception at startup

Issue

• We always experience the following Null Pointer Exception at Liferay startup:
  

  Caused by: java.lang.NullPointerException
      at com.liferay.portal.service.impl.ThemeLocalServiceImpl.getColorScheme(ThemeLocalServiceImpl.java:129)

Environment

• DXP 7.3

Resolution

• To solve this issue remove the following property upgrade.database.auto.run=true from your portal-ext.properties.
• An alternative way to eliminate this behavior is to upgrade to Liferay DXP 7.4.

Additional Information

• Auto-Upgrade in DXP 7.3 and Above