Issue Summary

Error thrown in assets import when the object key is mapped in the import configuration, however not present (empty) in the source file.

Steps to Reproduce

1. Create a csv import on your schema.
2. Setup the import mapping configuration as follows:
   
3. Have the following data in your csv, for example, and start the import.

   Key,Name
   ,Myobjectname

Expected Results

Even not having a key specified in the csv file, the object should be created.

Actual Results

The object isn't created and the following error appears in the import history:

Workaround

Creating a new import without mapping the key and remove that column from the csv file as well.