Oracle connection error

this the error:

Feedback Type:
Frown (Error)

Error Message:
Object reference not set to an instance of an object.

Stack Trace:
System.NullReferenceException
at Microsoft.PowerBI.Client.Windows.PowerBIQueryStalenessEvaluator.IsLoadRequired(Report report, Boolean includePendingUpgrades)
at Microsoft.PowerBI.Client.Windows.Services.WarningDetectionService.DetectReportLoadWarning()
at Microsoft.PowerBI.Client.Windows.Services.WarningDetectionService.<ScheduleAsyncDetection>b__40_1()
at Microsoft.Mashup.Host.Document.ExceptionHandlerExtensions.HandleExceptions(IExceptionHandler exceptionHandler, Action action)

Stack Trace Message:
Object reference not set to an instance of an object.

Invocation Stack Trace:
at Microsoft.Mashup.Host.Document.ExceptionExtensions.GetCurrentInvocationStackTrace()
at Microsoft.Mashup.Client.UI.Shared.StackTraceInfo..ctor(String exceptionStackTrace, String invocationStackTrace, String exceptionMessage)
at Microsoft.PowerBI.Client.Windows.Telemetry.PowerBIUserFeedbackServices.GetStackTraceInfo(Exception e)
at Microsoft.PowerBI.Client.Windows.Telemetry.PowerBIUserFeedbackServices.ReportException(IWindowHandle activeWindow, IUIHost uiHost, FeedbackPackageInfo feedbackPackageInfo, Exception e, Boolean useGDICapture)
at Microsoft.Mashup.Client.UI.Shared.UnexpectedExceptionHandler.<>c__DisplayClass14_0.<HandleException>b__0()
at Microsoft.Mashup.Host.Document.SynchronizationContextExtensions.<>c__DisplayClass2_0.<SendAndMarshalExceptions>b__0(Object null)
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbacks()
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
at System.Windows.Forms.WindowsFormsSynchronizationContext.Send(SendOrPostCallback d, Object state)
at Microsoft.Mashup.Host.Document.SynchronizationContextExtensions.SendAndMarshalExceptions(SynchronizationContext context, Action callback)
at Microsoft.Mashup.Client.UI.Shared.UnexpectedExceptionHandler.HandleException(Exception e)
at Microsoft.PowerBI.Client.PowerBIUnexpectedExceptionHandler.HandleException(Exception e)
at Microsoft.PowerBI.Client.Windows.Utilities.PowerBIFormUnexpectedExceptionHandler.HandleException(Exception e)
at Microsoft.Mashup.Host.Document.ExceptionHandlerExtensions.HandleExceptions(IExceptionHandler exceptionHandler, Action action)
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbacks()
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
at System.Windows.Forms.WindowsFormsSynchronizationContext.Send(SendOrPostCallback d, Object state)
at Microsoft.Mashup.Host.Document.SynchronizationContextExtensions.SendAndMarshalExceptions(SynchronizationContext context, Action callback)
at Microsoft.Mashup.Host.Document.ExceptionHandlerExtensions.HandleExceptions(IExceptionHandler exceptionHandler, Action action)
at Microsoft.PowerBI.Client.Windows.Services.EventAggregationService.Publish[TEvent,TEventArg](TEventArg eventArgs)
at Microsoft.PowerBI.Client.Telemetry.PowerBITelemetryManager.UpdateTelemetryConfiguration(PowerBITelemetryConfiguration newConfiguration, String callerName)
at Microsoft.PowerBI.Client.Telemetry.PowerBITelemetryManager.OnTracingEnabledChanged()
at Microsoft.PowerBI.Client.Windows.PowerBIApplicationTracingHost.set_TracingEnabled(Boolean value)
at Microsoft.PowerBI.Client.Telemetry.PowerBITelemetryManager.Dispose()
at Microsoft.PowerBI.Client.Program.RunApplication(String[] args)
at Microsoft.PowerBI.Client.Program.Main(String[] args)

PowerBINonFatalError:
{"AppName":"PBIDesktop","AppVersion":"2.124.1805.0","ModuleName":"Microsoft.PowerBI.Client.Windows.dll","Component":"Microsoft.PowerBI.Client.Windows.PowerBIQueryStalenessEvaluator","Error":"System.NullReferenceException","MethodDef":"IsLoadRequired","ErrorOffset":"0","ErrorCode":""}

PowerBIUserFeedbackServices_IsReported:
True