Cherry-pick 1004779. rdar://123745437

    [WebGPU] WebGPU::setUncapturedScopeCallback may crash if repeatedly invoked
    https://bugs.webkit.org/show_bug.cgi?id=270244
    <radar://123745437>

    Reviewed by Dan Glastonbury.

    We can only call this once, so null-out the callback
    after it has been called.

    * Source/WebGPU/WebGPU/Device.mm:
    (WebGPU::Device::generateAValidationError):

    Canonical link: https://commits.webkit.org/275478@main

Canonical link: https://commits.webkit.org/274941.58@safari-7619.1.5-branch

Source/WebGPU/WebGPU/Device.mm

@@ -305,8 +305,10 @@ static void captureFrame(id<MTLDevice> captureObject)
         return;
     }
 
-    if (m_uncapturedErrorCallback)
+    if (m_uncapturedErrorCallback) {
         m_uncapturedErrorCallback(WGPUErrorType_Validation, WTFMove(message));
+        m_uncapturedErrorCallback = nullptr;
+    }
 }
 
 void Device::generateAnOutOfMemoryError(String&& message)