The Error ORA-01400 means that there is an issue with data where the target column is defined as not null and data supplid has null for that column. Nothing to do with PK-FK relationship.
Looks like you have the BODS repository created in ORACLE.
The table AL_FKPKREL has an index AL_FKPKREL_INDX1 that has columns PKTABLE_NAME, PKTABLE_OWNER and PKCOLUMN_NAME in the index definition.
So the table metadata you are importing is not pulling through information the PK-FK relationship information in full. Below is the table and index structure for this table in the BODS repositoriy (Designer version 14.1.x).
Please check the table definition of the table that your trying to import.
kind regards
Raghu