[integration automatic-import] Small bugfixes (#188778)

This PR fixes two bugs that were causing failures leading to recursion
timeouts when generating integrations:

1) Small prompt tweak to the related prompt instruction the LLM to
include the if condition inside the processor
2) Followup fix to https://github.com/elastic/kibana/pull/187643 to also
include a field null check on the processor

x-pack/plugins/integration_assistant/__jest__/fixtures/ecs_mapping.ts

@@ -91,7 +91,7 @@ export const ecsMappingExpectedResults = {
           description: 'Ensures the date processor does not receive an array value.',
           lang: 'painless',
           source:
-            'if (ctx.mysql_enterprise.audit.timestamp instanceof ArrayList){\n    ctx.mysql_enterprise.audit.timestamp = ctx.mysql_enterprise.audit.timestamp[0];\n}\n',
+            'if (ctx.mysql_enterprise?.audit?.timestamp != null &&\n    ctx.mysql_enterprise.audit.timestamp instanceof ArrayList){\n    ctx.mysql_enterprise.audit.timestamp = ctx.mysql_enterprise.audit.timestamp[0];\n}\n',
           tag: 'script_convert_array_to_string',
         },
       },

x-pack/plugins/integration_assistant/server/graphs/related/prompts.ts

@@ -37,6 +37,7 @@ export const RELATED_MAIN_PROMPT = ChatPromptTemplate.fromMessages([
   - You can add as many append processors you need to cover all the fields that you detected.
   - If conditions should always use a ? character when accessing nested fields, in case the field might not always be available, see example processors above.
   - When an if condition is not needed the argument should not be used for the processor object.
+  - The if condition must be located within the processor object.
   - Do not respond with anything except the array of processors as a valid JSON objects enclosed with 3 backticks (\`), see example response below.
   </guidelines>
   

x-pack/plugins/integration_assistant/server/templates/pipeline.yml.njk

@@ -32,7 +32,8 @@ processors:
       tag: script_convert_array_to_string
       lang: painless
       {% raw %}source: |
-        if (ctx.{% endraw %}{{ value.field }}{% raw %} instanceof ArrayList){
+        if (ctx.{% endraw %}{{ value.field.replaceAll('.', '?.') }}{% raw %} != null &&
+            ctx.{% endraw %}{{ value.field }}{% raw %} instanceof ArrayList){
             ctx.{% endraw %}{{ value.field }}{% raw %} = ctx.{% endraw %}{{ value.field }}{% raw %}[0];
         }{% endraw %}
   - {{ key }}: