NullReferenceException: 未将对象引用设置到对象的实例。
StackTrace:
   在 MS.Internal.TextFormatting.TextMetrics.FullTextLine.FormatLine(FullTextState fullText, Int32 cpFirst, Int32 lineLength, Int32 formatWidth, Int32 finiteFormatWidth, Int32 paragraphWidth, LineFlags lineFlags, FormattedTextSymbols collapsingSymbol)
   在 MS.Internal.TextFormatting.TextMetrics.FullTextLine..ctor(FormatSettings settings, Int32 cpFirst, Int32 lineLength, Int32 paragraphWidth, LineFlags lineFlags)
   在 MS.Internal.TextFormatting.TextFormatterImp.FormatLineInternal(TextSource textSource, Int32 firstCharIndex, Int32 lineLength, Double paragraphWidth, TextParagraphProperties paragraphProperties, TextLineBreak previousLineBreak, TextRunCache textRunCache)
   在 MS.Internal.TextFormatting.TextFormatterImp.FormatLine(TextSource textSource, Int32 firstCharIndex, Double paragraphWidth, TextParagraphProperties paragraphProperties, TextLineBreak previousLineBreak, TextRunCache textRunCache)
   在 System.Windows.Controls.TextBlock.MeasureOverride(Size constraint)
   在 System.Windows.FrameworkElement.MeasureCore(Size availableSize)
   在 System.Windows.UIElement.Measure(Size availableSize)
   在 System.Windows.ContextLayoutManager.UpdateLayout()
   在 System.Windows.ContextLayoutManager.UpdateLayoutCallback(Object arg)
   在 System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks()
   在 System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
   在 System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget)
   在 System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   在 System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

NullReferenceException: 未将对象引用设置到对象的实例。
StackTrace:
   在 MS.Internal.TextFormatting.TextStore.CreateLineBreakLSRun(TextRunInfo runInfo, Int32 stringLength, Int32& lsrunLength, Int32& textRunLength)
   在 MS.Internal.TextFormatting.TextStore.CreateLSRuns(TextRunInfo runInfo, IList`1 textEffects, CultureInfo digitCulture, Int32 offsetToFirstChar, Int32 stringLength, Int32 uniformBidiLevel, TextFormattingMode textFormattingMode, Boolean isSideways, Int32& lastBidiLevel, Int32& textRunLength)
   在 MS.Internal.TextFormatting.TextStore.CreateLSRunsUniformBidiLevel(SpanVector runInfoVector, SpanVector textEffectsVector, Int32 runInfoFirstCp, Int32 ichUniform, Int32 cchUniform, Int32 uniformBidiLevel, TextFormattingMode textFormattingMode, Boolean isSideways, Int32& lastBidiLevel)
   在 MS.Internal.TextFormatting.TextStore.FetchLSRun(Int32 lscpFetch, TextFormattingMode textFormattingMode, Boolean isSideways, Plsrun& plsrun, Int32& lsrunOffset, Int32& lsrunLength)
   在 MS.Internal.TextFormatting.LineServicesCallbacks.FetchRunRedefined(IntPtr pols, Int32 lscpFetch, Int32 fIsStyle, IntPtr pstyle, Char* pwchTextBuffer, Int32 cchTextBuffer, Int32& fIsBufferUsed, Char*& pwchText, Int32& cchText, Int32& fIsHidden, LsChp& lschp, IntPtr& lsplsrun)