How can i fix Index Out Of Range Exception of a char?

First the project it self i didn't do it i took it from github:

spazzarama/Direct3DHook

The problem the exception happen when i try to use any directx11 game. The exception happen in the DXHookD3D11.cs

#region Draw overlay (after screenshot so we don't capture overlay as well)
                if (this.Config.ShowOverlay)
                {
                    // Initialise Overlay Engine
                    if (_swapChainPointer != swapChain.NativePointer || _overlayEngine == null)
                    {
                        if (_overlayEngine != null)
                            _overlayEngine.Dispose();

                        _overlayEngine = new DX11.DXOverlayEngine();
                        _overlayEngine.Overlays.Add(new Capture.Hook.Common.Overlay
                        {
                            Elements =
                            {
                                //new Capture.Hook.Common.TextElement(new System.Drawing.Font("Times New Roman", 22)) { Text = "Test", Location = new System.Drawing.Point(200, 200), Color = System.Drawing.Color.Yellow, AntiAliased = false},
                                new Capture.Hook.Common.FramesPerSecond(new System.Drawing.Font("Arial", 16)) { Location = new System.Drawing.Point(5,5), Color = System.Drawing.Color.Red, AntiAliased = true }
                            }
                        });
                        _overlayEngine.Initialise(swapChain);

                        _swapChainPointer = swapChain.NativePointer;
                    }
                    // Draw Overlay(s)
                    else if (_overlayEngine != null)
                    {
                        foreach (var overlay in _overlayEngine.Overlays)
                            overlay.Frame();
                        _overlayEngine.Draw();
                    }
                }
                #endregion

Then when it's trying to Draw() i used a breakpoint it's going to the class DXOverlayEngine.cs to this line:

_spriteEngine.DrawString(textElement.Location.X, textElement.Location.Y, textElement.Text, textElement.Color.R, textElement.Color.G, textElement.Color.B, textElement.Color.A, font);

Then it's going to the DXSprite.cs to this part:

public void DrawString(int X, int Y, string text, int R, int G, int B, int A, DXFont F)
        {
            Color4 blendFactor = new Color4(1.0f);
            Color4 backupBlendFactor;
            int backupMask;
            var backupBlendState = _deviceContext.OutputMerger.GetBlendState(out backupBlendFactor, out backupMask);
            _deviceContext.OutputMerger.SetBlendState(_transparentBS, blendFactor);

            BeginBatch(F.GetFontSheetSRV());


            int length = text.Length;

            int posX = X;
            int posY = Y;

            Color4 color;
            Vector4 Vec = new Vector4(R > 0 ? (float)(R / 255.0f) : 0.0f, G > 0 ? (float)(G / 255.0f) : 0.0f, B > 0 ? (float)(B / 255.0f) : 0.0f, A > 0 ? (float)(A / 255.0f) : 0.0f);
            color = new Color4(Vec);

            for (int i = 0; i < length; ++i)
            {
                char character = text[i];

                if (character == ' ')
                    posX += F.GetSpaceWidth();
                else if (character == '\n')
                {
                    posX = X;
                    posY += F.GetCharHeight();
                }
                else
                {
                    Rectangle charRect = F.GetCharRect(character);

And last it's doing the line F.GetCharRect(character) in the DXFont.cs class:

public Rectangle GetCharRect(char c)
        {
            Debug.Assert(_initialized);

            return _charRects[c - StartChar];
        }

I used a breakpoint on the method GetCharRect and for example in this case the variable c value is: 163'£ and the value in the variable StartChar is 33 '!'

Then it's showing the exception on the line:

return _charRects[c - StartChar];

I tried to ask the owner about this problem and so far all he told me is:

"Sounds like it is trying to draw a character that it hasn't prepared..."

I tried to narrow the code here as much as i can but it's all connect each other.