Fix nil crash when job has no fields defined (#2776)

## Changes
Add missing nil checks in normalize_paths.go

## Tests
Tests added previously in #2771 and #2774

Author: denik

acceptance/bundle/validate/empty_resources/empty_dict/output.txt

@@ -1,14 +1,12 @@
 
 === resources.jobs.rname ===
-The Databricks CLI unexpectedly had a fatal error.
-Please report this issue to Databricks in the form of a GitHub issue at:
-https://github.com/databricks/cli
+Error: job rname is not defined
 
-CLI Version: [DEV_VERSION]
-
-Panic Payload: runtime error: invalid memory address or nil pointer dereference
-
-<Stack Trace>
+{
+  "jobs": {
+    "rname": {}
+  }
+}
 
 === resources.pipelines.rname ===
 Error: pipeline rname is not defined

acceptance/bundle/validate/empty_resources/test.toml

@@ -1,14 +1,16 @@
 
 === resources.jobs.rname ===
-The Databricks CLI unexpectedly had a fatal error.
-Please report this issue to Databricks in the form of a GitHub issue at:
-https://github.com/databricks/cli
-
-CLI Version: [DEV_VERSION]
+Warning: unknown field: grants
+  at resources.jobs.rname
+  in databricks.yml:7:7
 
-Panic Payload: runtime error: invalid memory address or nil pointer dereference
+Error: job rname is not defined
 
-<Stack Trace>
+{
+  "jobs": {
+    "rname": {}
+  }
+}
 
 === resources.pipelines.rname ===
 Warning: unknown field: grants

acceptance/bundle/validate/empty_resources/with_grants/output.txt

@@ -1,14 +1,14 @@
 
 === resources.jobs.rname ===
-The Databricks CLI unexpectedly had a fatal error.
-Please report this issue to Databricks in the form of a GitHub issue at:
-https://github.com/databricks/cli
+Error: job rname is not defined
 
-CLI Version: [DEV_VERSION]
-
-Panic Payload: runtime error: invalid memory address or nil pointer dereference
-
-<Stack Trace>
+{
+  "jobs": {
+    "rname": {
+      "permissions": []
+    }
+  }
+}
 
 === resources.pipelines.rname ===
 Error: pipeline rname is not defined

acceptance/bundle/validate/empty_resources/with_permissions/output.txt

@@ -72,6 +72,9 @@ func collectGitSourcePaths(b *bundle.Bundle) []dyn.Path {
 	var jobs []dyn.Path
 
 	for name, job := range b.Config.Resources.Jobs {
+		if job == nil || job.JobSettings == nil {
+			continue
+		}
 		if job.GitSource != nil {
 			jobs = append(jobs, dyn.NewPath(dyn.Key("resources"), dyn.Key("jobs"), dyn.Key(name)))
 		}