util: check for null instead of flasy in loop

This prepares the code for the no-cond-assign ESLint rule.

PR-URL: #41614
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: Trott

lib/internal/util/inspect.js

@@ -1311,7 +1311,7 @@ function formatError(err, constructor, tag, ctx, keys) {
           let nodeModule;
           newStack += '\n';
           let pos = 0;
-          while (nodeModule = nodeModulesRegExp.exec(line)) {
+          while ((nodeModule = nodeModulesRegExp.exec(line)) !== null) {
             // '/node_modules/'.length === 14
             newStack += line.slice(pos, nodeModule.index + 14);
             newStack += ctx.stylize(nodeModule[1], 'module');