fix: Handle null and undefined in manual console output (#41570)

Co-authored-by: n8n-cat-bot[bot] <n8n-cat-bot[bot]@users.noreply.github.com>

packages/core/src/execution-engine/node-execution-context/__tests__/execute-context.test.ts

@@ -254,6 +254,46 @@ describe('ExecuteContext', () => {
 	});
 
 	describe('logNodeOutput', () => {
+		// NODE-5746: Forward valid Code node logs to the editor without server warnings.
+		it.each([
+			{ logCall: 'console.log("x", 42)', args: ['x', 42], messages: ['x', 42] },
+			{ logCall: 'console.log(null)', args: [null], messages: ['null'] },
+			{ logCall: 'console.log(undefined)', args: [undefined], messages: ['undefined'] },
+			{ logCall: 'console.log("x", null)', args: ['x', null], messages: ['x', 'null'] },
+		])(
+			'should forward $logCall to the editor in manual mode without warnings',
+			({ args, messages }) => {
+				const sendDataToUI = vi.fn();
+				const codeNode = mock<INode>({
+					name: 'Code',
+					type: 'n8n-nodes-base.code',
+					typeVersion: 2,
+				});
+				const context = new ExecuteContext(
+					mock<Workflow>({ settings: { redactionPolicy: 'none' } }),
+					codeNode,
+					mock<IWorkflowExecuteAdditionalData>({ sendDataToUI }),
+					'manual',
+					mock<IRunExecutionData>(),
+					runIndex,
+					connectionInputData,
+					inputData,
+					executeData,
+					[],
+				);
+				const warnSpy = vi.spyOn(context.logger, 'warn').mockImplementation(() => {});
+
+				context.logNodeOutput(...args);
+
+				expect.soft(warnSpy).not.toHaveBeenCalled();
+				expect(sendDataToUI).toHaveBeenCalledTimes(1);
+				expect(sendDataToUI).toHaveBeenCalledWith('sendConsoleMessage', {
+					source: '[Node: "Code"]',
+					messages,
+				});
+			},
+		);
+
 		it('when in manual mode, should parse JSON', () => {
 			const json = '{"key": "value", "nested": {"foo": "bar"}}';
 			const expectedParsedObject = { key: 'value', nested: { foo: 'bar' } };

packages/core/src/execution-engine/node-execution-context/base-execute-context.ts

@@ -425,6 +425,8 @@ export class BaseExecuteContext extends NodeExecutionContext {
 		try {
 			if (this.additionalData.sendDataToUI) {
 				args = args.map((arg) => {
+					if (arg === null || arg === undefined) return String(arg);
+
 					// prevent invalid dates from being logged as null
 					// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-return
 					if (arg.isLuxonDateTime && arg.invalidReason) return { ...arg };