Fix failing of functions without revert code

Add missing empty/undefined handling to fix a bug where defining new
functions without `revertCode:` fails.

src/application/Parser/Script/Compiler/Expressions/ExpressionsCompiler.ts

@@ -10,11 +10,14 @@ export class ExpressionsCompiler implements IExpressionsCompiler {
     public constructor(
         private readonly extractor: IExpressionParser = new CompositeExpressionParser()) { }
     public compileExpressions(
-        code: string,
+        code: string | undefined,
         args: IReadOnlyFunctionCallArgumentCollection): string {
         if (!args) {
             throw new Error('undefined args, send empty collection instead');
         }
+        if (!code) {
+            return code;
+        }
         const expressions = this.extractor.findExpressions(code);
         ensureParamsUsedInCodeHasArgsProvided(expressions, args);
         const context = new ExpressionEvaluationContext(args);

src/application/Parser/Script/Compiler/Expressions/IExpressionsCompiler.ts

@@ -2,6 +2,6 @@ import { IReadOnlyFunctionCallArgumentCollection } from '../Function/Call/Argume
 
 export interface IExpressionsCompiler {
     compileExpressions(
-        code: string,
+        code: string | undefined,
         args: IReadOnlyFunctionCallArgumentCollection): string;
 }

src/application/Parser/Script/Compiler/Expressions/Parser/Regex/RegexParser.ts

@@ -15,6 +15,9 @@ export abstract class RegexParser implements IExpressionParser {
     protected abstract buildExpression(match: RegExpMatchArray): IPrimitiveExpression;
 
     private* findRegexExpressions(code: string): Iterable<IExpression> {
+        if (!code) {
+            throw new Error('undefined code');
+        }
         const matches = Array.from(code.matchAll(this.regex));
         for (const match of matches) {
             const startPos = match.index;