optional modules will not fail the build when bail is set

fixes #11594

lib/Compilation.js

@@ -1574,10 +1574,11 @@ BREAKING CHANGE: Asset processing hooks in Compilation has been merged into a si
 				if (err) {
 					if (dependencies.every(d => d.optional)) {
 						this.warnings.push(err);
+						return callback();
 					} else {
 						this.errors.push(err);
+						return callback(err);
 					}
-					return callback(err);
 				}
 
 				if (!newModule) {

test/configCases/parsing/optional/index.js

@@ -0,0 +1,11 @@
+it("should not fail for optional modules with bail", () => {
+	let error;
+	try {
+		require("./not-existing");
+	} catch (e) {
+		error = e;
+	}
+	expect(() => {
+		throw error;
+	}).toThrowError();
+});

test/configCases/parsing/optional/warnings.js

@@ -0,0 +1,7 @@
+module.exports = [
+	[
+		/Module not found/,
+		/Can't resolve '\.\/not-existing' /,
+		{ details: /not-existing\.js/ }
+	]
+];

test/configCases/parsing/optional/webpack.config.js

@@ -0,0 +1,4 @@
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	bail: true
+};