Don't try to create a framebuffer of size 0.

src/Windows/Avalonia.Win32/FramebufferManager.cs

@@ -25,7 +25,7 @@ namespace Avalonia.Win32
             UnmanagedMethods.GetClientRect(_hwnd, out rc);
             var width = rc.right - rc.left;
             var height = rc.bottom - rc.top;
-            if (_fb == null || _fb.Width != width || _fb.Height != height)
+            if ((_fb == null || _fb.Width != width || _fb.Height != height) && width > 0 && height > 0)
             {
                 _fb?.Deallocate();
                 _fb = null;