cmd/cue/cmd: fix crash

Fixes #261

Change-Id: If014a03a5c000b4e8ed90956d76664238e59f60d
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/4701
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/cmd/cue/cmd/vet.go b/cmd/cue/cmd/vet.go
index 946f34f..28cab4d 100644
--- a/cmd/cue/cmd/vet.go
+++ b/cmd/cue/cmd/vet.go
@@ -178,7 +178,7 @@
 		r := internal.GetRuntime(inst).(*cue.Runtime)
 		for _, expr := range exprs {
 			body, err := r.CompileExpr(expr)
-			exitIfErr(cmd, inst, err, false)
+			exitIfErr(cmd, inst, err, true)
 			v := body.Value().Unify(check)
 			if err := v.Err(); err != nil {
 				exitIfErr(cmd, inst, err, false)