Revert initial tab changes and invert tab fallbacks

ee/app/assets/javascripts/threat_monitoring/components/policy_editor/policy_drawer.vue

@@ -15,6 +15,9 @@ export default {
     },
   },
   computed: {
+    initialTab() {
+      return this.policy ? 0 : 1;
+    },
     policy() {
       const policy = fromYaml(this.value);
       return policy.error ? null : policy;
@@ -49,6 +52,7 @@ export default {
 
     <policy-preview
       class="gl-mt-4"
+      :initial-tab="initialTab"
       :policy-yaml="policyYaml"
       :policy-description="humanizedPolicy"
     />

ee/spec/frontend/threat_monitoring/components/policy_editor/__snapshots__/policy_drawer_spec.js.snap

@@ -70,7 +70,7 @@ exports[`PolicyDrawer component unsupported YAML renders policy preview tabs 1`]
    
   <policy-preview-stub
     class="gl-mt-4"
-    initialtab="0"
+    initialtab="1"
     policyyaml="unsupportedPrimaryKey: test"
   />
 </div>

ee/spec/frontend/threat_monitoring/components/policy_editor/policy_drawer_spec.js

@@ -68,7 +68,7 @@ describe('PolicyDrawer component', () => {
     it('does render the policy preview', () => {
       expect(findPolicyPreview().exists()).toBe(true);
       expect(findPolicyPreview().props()).toStrictEqual({
-        initialTab: 0,
+        initialTab: 1,
         policyDescription: null,
         policyYaml: unsupportedYaml,
       });