chore: abort if match strings are empty

lib/modules/manager/regex/index.spec.ts

@@ -323,6 +323,19 @@ describe('modules/manager/regex/index', () => {
     expect(res).toBeNull();
   });
 
+  it('return with recursive strategy if matchStrings is empty', async () => {
+    const config: CustomExtractConfig = {
+      matchStrings: [],
+      matchStringsStrategy: 'recursive',
+    };
+    const res = await extractPackageFile(
+      exampleJsonContent,
+      'example.json',
+      config
+    );
+    expect(res).toBeNull();
+  });
+
   it('extracts with recursive strategy and single match', async () => {
     const config: CustomExtractConfig = {
       matchStrings: [

lib/modules/manager/regex/strategies.ts

@@ -61,6 +61,11 @@ export function handleRecursive(
   const regexes = config.matchStrings.map((matchString) =>
     regEx(matchString, 'g')
   );
+
+  if (!regexes.length) {
+    return [];
+  }
+
   // abort if we have no matchString anymore
   if (!regexes[index]) {
     const result = createDependency(
@@ -82,5 +87,6 @@ export function handleRecursive(
         mergeGroups(combinedGroups, match.groups ?? {})
       );
     })
+    .filter(is.truthy)
     .filter(isValidDependency);
 }