5d6dbfb0879ab769c41f832feb2a1a83415ea0f5
max
  Fri Nov 14 07:12:22 2025 -0800
avoid error message when igv button is not found, refs #36673

diff --git src/hg/js/igvFileHelper.js src/hg/js/igvFileHelper.js
index dc8f20ee025..0c30066a0ab 100644
--- src/hg/js/igvFileHelper.js
+++ src/hg/js/igvFileHelper.js
@@ -341,31 +341,35 @@
     }
 
     function stopSessionAutoSave() {
         if (sessionAutoSaveTimer !== null) {
             clearInterval(sessionAutoSaveTimer);
             sessionAutoSaveTimer = null;
         }
     }
 
 
     window.addEventListener("DOMContentLoaded", async () => {
 
         // The "Add IGV track" button handler.  The button opens the file picker window, unless
         // it is already open in which case it brings that window to the front.  Tracks are added
         // from the filePicker page by selecting track files.
-        document.getElementById('hgtIgv').addEventListener('click', async function (e) {
+        let butEl = document.getElementById('hgtIgv');
+        if (butEl===null) // can only happen if page crashes, helps avoid distract engineer's attention
+            return;
+
+        butEl.addEventListener('click', async function (e) {
             e.preventDefault(); // our
             if (filePicker && !filePicker.closed) {
                 showDialog("To add tracks please use the existing IGV File Manager window.");
                 filePicker.focus();
                 return;
             } else {
                 // A file picker may be open from a previous session. First ping it to see if it is still there,
                 // if it responds the user should be alerted, if needed,  from a failed track load.
                 const responded = await pingFilePicker();
                 if (responded) {
                     showDialog("To add tracks please use the existing IGV File Manager window.");
                 } else {
                     showDialog("To add tracks please use the IGV File Manager window.");
                     filePicker = openFilePicker();
                 }