Fixed null pointer de-reference if artifacts missing fields (#3022)

## Changes
Fixed null pointer de-reference if artifacts missing fields

## Why
Fixes #3017 

## Tests
Added regression test

<!-- If your PR needs to be included in the release notes for next
release,
add a separate entry in NEXT_CHANGELOG.md as part of your PR. -->

Author: andrewnester

NEXT_CHANGELOG.md

@@ -13,5 +13,6 @@
 
 ### Bundles
 * Fix "bundle summary -o json" to render null values properly ([#2990](https://github.com/databricks/cli/pull/2990))
+* Fixed null pointer de-reference if artifacts missing fields ([#3022](https://github.com/databricks/cli/pull/3022))
 
 ### API Changes

acceptance/bundle/artifacts/nil_artifacts/databricks.yml

@@ -0,0 +1,10 @@
+bundle:
+  name: nil_artifacts_test
+
+artifacts:
+  # This reproduces the issue from GitHub #3017
+  # where artifacts have empty definitions (only comments)
+  my_artifact:
+    # build: <first_option_command>
+    # path: <path>
+    # build: <second_option_command>

acceptance/bundle/artifacts/nil_artifacts/output.txt

@@ -0,0 +1,16 @@
+
+>>> [CLI] bundle validate
+Error: Artifact not properly configured
+  in databricks.yml:7:15
+
+please specify artifact properties
+
+Name: nil_artifacts_test
+Target: default
+Workspace:
+  User: [USERNAME]
+  Path: /Workspace/Users/[USERNAME]/.bundle/nil_artifacts_test/default
+
+Found 1 error
+
+Exit code: 1

acceptance/bundle/artifacts/nil_artifacts/script

@@ -0,0 +1 @@
+errcode trace $CLI bundle validate

acceptance/bundle/artifacts/nil_artifacts/test.toml

@@ -0,0 +1,9 @@
+RecordRequests = false
+
+[[Repls]]
+Old = '\\\\'
+New = '/'
+
+[[Repls]]
+Old = '\\'
+New = '/'

bundle/artifacts/prepare.go

@@ -10,6 +10,7 @@ import (
 	"github.com/databricks/cli/bundle/libraries"
 	"github.com/databricks/cli/bundle/metrics"
 	"github.com/databricks/cli/libs/diag"
+	"github.com/databricks/cli/libs/dyn"
 	"github.com/databricks/cli/libs/log"
 	"github.com/databricks/cli/libs/python"
 	"github.com/databricks/cli/libs/utils"
@@ -35,6 +36,16 @@ func (m *prepare) Apply(ctx context.Context, b *bundle.Bundle) diag.Diagnostics
 
 	for _, artifactName := range utils.SortedKeys(b.Config.Artifacts) {
 		artifact := b.Config.Artifacts[artifactName]
+		if artifact == nil {
+			l := b.Config.GetLocation("artifacts." + artifactName)
+			diags = append(diags, diag.Diagnostic{
+				Severity:  diag.Error,
+				Summary:   "Artifact not properly configured",
+				Detail:    "please specify artifact properties",
+				Locations: []dyn.Location{l},
+			})
+			continue
+		}
 		b.Metrics.AddBoolValue(metrics.ArtifactBuildCommandIsSet, artifact.BuildCommand != "")
 		b.Metrics.AddBoolValue(metrics.ArtifactFilesIsSet, len(artifact.Files) != 0)