I don't know why you would get that diagnostic.  CA Sch D is not a requirement for e-filing; so, I have NO clue why your efiling wouldn't go thru without the CA Sch D.  It doesn't make sense to me from the angle of CA tax e-file processing.

Entering -1 for the state amount would trigger Sch D for CA - yes - but if your client had CA source income or CA tax, the CA tax computation would be off/wrong.  Basically CA NR tax is computed based on the percentage of CA source income applied to the CA tax (Line 31 on 540NR).  By entering -1, you would change the computation of Line 31. 

However, if your client didn't have significant CA tax, who cares, right?     

If the accuracy for your client's CA tax is important, consider changing the state number by $1 instead of entering -1.