Show error in box if one is available

Summary: Add a check to prevent the odd error when the box is no longer available to display an error.

Reviewed By: antonk52

Differential Revision: D46763634

fbshipit-source-id: 6ac2c404c842ff989b037c991b5f085baacd2f9a

desktop/static/index.dev.html

@@ -81,8 +81,10 @@
         }
 
         const box = document.querySelector('.__infinity-dev-box-error');
-        box.removeAttribute('hidden');
-        box.textContent = text;
+        if (box) {
+          box.removeAttribute('hidden');
+          box.textContent = text;
+        }
       }
 
       // load correct theme (n.b. this doesn't handle system value specifically, will assume light in such cases)

desktop/static/index.web.dev.html

@@ -109,7 +109,9 @@
           }
 
           const box = document.getElementById('loading');
-          box.textContent = text;
+          if (box) {
+            box.textContent = text;
+          }
         }
         window.flipperShowError = openError;