java.lang.NullPointerException: while trying to invoke the method com.sap.isa.core.eai.BackendConfig.getId() of a null object

I'm migrating a SAP B2B Commerce project from version 7.0 to 7.4, with the previous version of java 1.4 to 1.7.

I can't see the login page, instead i see this 500 Internal Server Error message:

Error: ISA Framework: javax.servlet.ServletException: java.lang.NullPointerException: while trying to invoke the method com.sap.isa.core.eai.BackendConfig.getId() of a null object loaded from local variable 'config'

But after a search in my files, i never see the variable 'config' or the com.sap.isa.core.eai.BackendConfig import.

Where is the problem located? and how i can solve this issue? is this problem is unrelated to my components?