fix: automation form validation

apps/client/src/features/app-settings/panel/automations-panel/AutomationForm.tsx

@@ -230,13 +230,18 @@ export default function AutomationForm({ automation, onClose }: AutomationFormPr
               <div key={key} className={style.filterSection}>
                 <label>
                   Runtime data source
-                  <Select
-                    value={watch(`filters.${index}.field`)}
-                    onValueChange={(value: string | null) => {
+                  <Select<string | null>
+                    // need to normalize '' to null for the Select to show the placeholder
+                    value={watch(`filters.${index}.field`) || null}
+                    onValueChange={(value) => {
                       if (value === null) return;
                       setValue(`filters.${index}.field`, value, { shouldDirty: true });
                     }}
-                    options={fieldList.map(({ value, label }) => ({ value, label }))}
+                    options={fieldList.map(({ value, label }) => ({
+                      value,
+                      label,
+                      disabled: value === null,
+                    }))}
                     aria-label='Event field'
                   />
                   <Panel.Error>{errors.filters?.[index]?.field?.message}</Panel.Error>
@@ -288,7 +293,8 @@ export default function AutomationForm({ automation, onClose }: AutomationFormPr
       <div className={style.innerColumn}>
         <h3>Outputs</h3>
         <Info>
-          Automation outputs can be used to send data from Ontime to external software.
+          Automation outputs can be used to send data from Ontime to external software <br />
+          or to change properties of Ontime itself.
           <ExternalLink href={integrationsDocsUrl}>See the documentation for templates</ExternalLink>
         </Info>