Enable the no-useless-catch ESLint rule

See https://eslint.org/docs/rules/no-useless-catch

.eslintrc

@@ -88,6 +88,7 @@
     "no-unused-expressions": "error",
     "no-unused-labels": "error",
     "no-useless-call": "error",
+    "no-useless-catch": "error",
     "no-useless-concat": "error",
     "prefer-promise-reject-errors": "error",
     "wrap-iife": ["error", "any"],

web/app.js

@@ -1621,17 +1621,13 @@ if (typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) {
       // cannot load file:-URLs in a Web Worker. file:-URLs are usually loaded
       // very quickly, so there is no need to set up progress event listeners.
       PDFViewerApplication.setTitleUsingUrl(file);
-      let xhr = new XMLHttpRequest();
+      const xhr = new XMLHttpRequest();
       xhr.onload = function() {
         PDFViewerApplication.open(new Uint8Array(xhr.response));
       };
-      try {
       xhr.open('GET', file);
       xhr.responseType = 'arraybuffer';
       xhr.send();
-      } catch (ex) {
-        throw ex;
-      }
       return;
     }