Fixing the crash due to callback is not provided.

(cherry picked from commit da60ee0)

Bug: b/229108783
Change-Id: I3f2c6575897c64c908795122e6b38d5a305638c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3586329
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Abbas Nayebi <nayebi@google.com>
Cr-Original-Commit-Position: refs/heads/main@{#992985}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3600679
Auto-Submit: Christine Franks <christyfranks@google.com>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/branch-heads/5005@{#125}
Cr-Branched-From: 5b4d945-refs/heads/main@{#992738}

chrome/browser/ash/attestation/soft_bind_attestation_flow.cc

@@ -135,6 +135,10 @@ const std::string& SoftBindAttestationFlow::Session::GetUserKey() const {
 
 void SoftBindAttestationFlow::Session::ReportFailure(
     const std::string& error_message) {
+  if (!callback_) {
+    LOG(ERROR) << "Attestation session failure callback in null.";
+    return;
+  }
   std::move(callback_).Run(
       std::vector<std::string>{"INVALID:" + error_message});
 }