Validate source before compiling CJS module. module: fix ERR_INTERNAL_ASSERTION in CJS module loading

Fixes: #60401

The loadCJSModule function was not properly validating source
content before passing it to compileFunctionForCJSLoader, causing internal assertions when source was null or undefined.

This change adds proper source validation and throws a meaningful ERR_INVALID_RETURN_PROPERTY_VALUE error instead of failing with an internal assertion.

Author: vivek958

lib/internal/modules/esm/translators.js

@@ -124,8 +124,21 @@ translators.set('module', function moduleStrategy(url, translateContext, parentU
  * @param {boolean} isMain - Whether the module is the entrypoint
  */
 function loadCJSModule(module, source, url, filename, isMain) {
-  const compileResult = compileFunctionForCJSLoader(source, filename, false /* is_sea_main */, false);
+  // Validate source before compilation to prevent internal assertion errors.
+  // Without this check, null or undefined source causes ERR_INTERNAL_ASSERTION
+  // when passed to compileFunctionForCJSLoader.
+  // Refs: https://github.com/nodejs/node/issues/60401
+  if (source == null || source === '') {
+    throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
+      'non-empty string',
+      'load',
+      'source',
+      source,
+    );
+  }
 
+  const compileResult = compileFunctionForCJSLoader(source, filename, false /* is_sea_main */, false);
+  
   const { function: compiledWrapper, sourceMapURL, sourceURL } = compileResult;
   // Cache the source map for the cjs module if present.
   if (sourceMapURL) {