LibJS: Handle empty named export

This is an export which looks like `export {} from "module"`, and
although it doesn't have any real export entries it should still add
"module" to the required modules to load.

Userland/Libraries/LibJS/Tests/modules/basic-modules.js

@@ -193,3 +193,25 @@ describe("loops", () => {
         expectModulePassed("./loop-entry.mjs");
     });
 });
+
+describe("failing modules cascade", () => {
+    let failingModuleError = "Left-hand side of postfix";
+    test("importing a file with a SyntaxError results in a SyntaxError", () => {
+        expectedModuleToThrowSyntaxError("./failing.mjs", failingModuleError);
+    });
+
+    test("importing a file without a syntax error which imports a file with a syntax error fails", () => {
+        expectedModuleToThrowSyntaxError("./importing-failing-module.mjs", failingModuleError);
+    });
+
+    test("importing a file which re exports a file with a syntax error fails", () => {
+        expectedModuleToThrowSyntaxError("./exporting-from-failing.mjs", failingModuleError);
+    });
+
+    test("importing a file re exports nothing from a file with a syntax error fails", () => {
+        expectedModuleToThrowSyntaxError(
+            "./exporting-nothing-from-failing.mjs",
+            failingModuleError
+        );
+    });
+});

Userland/Libraries/LibJS/Tests/modules/exporting-from-failing.mjs

@@ -0,0 +1 @@
+export * as shouldFail from "./failing.mjs";

Userland/Libraries/LibJS/Tests/modules/exporting-nothing-from-failing.mjs

@@ -0,0 +1,4 @@
+export {} from "./failing.mjs";
+export {};
+// This should not be a duplicate!
+export {} from "./failing.mjs";

Userland/Libraries/LibJS/Tests/modules/failing.mjs

@@ -0,0 +1,2 @@
+// Should produce a SyntaxError!
+0++;

Userland/Libraries/LibJS/Tests/modules/importing-failing-module.mjs

@@ -0,0 +1 @@
+import "./failing.mjs";