docs: fix description of _empty filter fields

Lists can never be null in cruddl. It also does not make sense to treat null as non-empty, and it was not the case.

Author: Yogu

src/schema-generation/filter-input-types/filter-fields.ts

@@ -247,7 +247,7 @@ export class EmptyListFilterField implements FilterField {
 
     constructor(public readonly field: Field) {
         this.name = this.field.name + '_empty';
-        this.description = `Checks if \`${this.field.name}\` is an empty list (true) or a non-empty list or null (false).`;
+        this.description = `Checks if \`${this.field.name}\` is an empty list (true) or a non-empty list (false).`;
     }
 
     getFilterNode(sourceNode: QueryNode, filterValue: AnyValue): QueryNode {

src/schema-generation/flex-search-filter-input-types/filter-fields.ts

@@ -319,7 +319,7 @@ export class FlexSearchEmptyListFilterField implements FlexSearchFilterField {
 
     constructor(public readonly field: Field) {
         this.name = this.field.name + '_empty';
-        this.description = `Checks if \`${this.field.name}\` is an empty list (true) or a non-empty list or null (false).`;
+        this.description = `Checks if \`${this.field.name}\` is an empty list (true) or a non-empty list (false).`;
     }
 
     getFilterNode(