[Security Solution][Exceptions] - Fix empty selection showing for exception item field selection (#155221)

## Summary

Addresses https://github.com/elastic/kibana/issues/145540

- blank space no longer shows as selection option for exception item
field dropdown

packages/kbn-securitysolution-autocomplete/src/field/__tests__/use_field.test.ts

@@ -84,7 +84,56 @@ describe('useField', () => {
       expect(comboOptions).toEqual([{ label: 'bytes' }, { label: 'ssl' }, { label: '@timestamp' }]);
       expect(selectedComboOptions).toEqual([]);
     });
-    it('should not return an empty field as a combo option', () => {
+    it('should not return a selected field when empty string as a combo option', () => {
+      const newIndexPattern = {
+        ...indexPattern,
+        fields: [
+          {
+            name: 'bytes',
+            type: 'number',
+            esTypes: ['long'],
+            count: 10,
+            scripted: false,
+            searchable: true,
+            aggregatable: true,
+            readFromDocValues: true,
+          },
+          {
+            name: 'ssl',
+            type: 'boolean',
+            esTypes: ['boolean'],
+            count: 20,
+            scripted: false,
+            searchable: true,
+            aggregatable: true,
+            readFromDocValues: true,
+          },
+          {
+            name: '@timestamp',
+            type: 'date',
+            esTypes: ['date'],
+            count: 30,
+            scripted: false,
+            searchable: true,
+            aggregatable: true,
+            readFromDocValues: true,
+          },
+        ] as unknown as DataViewFieldBase[],
+        title: 'title1',
+      };
+
+      const { result } = renderHook(() =>
+        useField({
+          indexPattern: newIndexPattern,
+          onChange: onChangeMock,
+          selectedField: { name: '', type: 'keyword' },
+        })
+      );
+      const { comboOptions, selectedComboOptions } = result.current;
+      expect(comboOptions).toEqual([{ label: 'bytes' }, { label: 'ssl' }, { label: '@timestamp' }]);
+      expect(selectedComboOptions).toEqual([]);
+    });
+    it('should not return a selected field when string with spaces is written as a combo option', () => {
       const newIndexPattern = {
         ...indexPattern,
         fields: [

packages/kbn-securitysolution-autocomplete/src/field/use_field.tsx

@@ -26,14 +26,13 @@ import {
   GetFieldComboBoxPropsReturn,
 } from './types';
 import { disabledTypesWithTooltipText } from './disabled_types_with_tooltip_text';
-import { paramContainsSpace } from '../param_contains_space';
 
 const getExistingFields = (indexPattern: DataViewBase | undefined): DataViewFieldBase[] => {
   return indexPattern != null ? indexPattern.fields : [];
 };
 
 const getSelectedFields = (selectedField: DataViewField | undefined): DataViewFieldBase[] => {
-  return selectedField && !paramContainsSpace(selectedField.name) ? [selectedField] : [];
+  return selectedField && selectedField.name.trim() !== '' ? [selectedField] : [];
 };
 
 const getAvailableFields = (