RemoteWidget stops rendering when width or height is equal to zero

[DrunkyBard]

Describe the bug
RemoteWidget throws an exception when window's width or height is equal to zero and stops to render any frames.

StackTrace:

System.ArgumentException: Positive number required (Parameter 'size')
at Avalonia.Shared.PlatformSupport.StandardRuntimePlatform.UnmanagedBlob..ctor(StandardRuntimePlatform plat, Int32 size) in C:\Avalonia\src\Shared\PlatformSupport\StandardRuntimePlatform.cs:line 56

To Reproduce
Steps to reproduce the behavior:

1. Launch RemoteDemo example
2. Resize window so width or height is equal to zero
3. RemoteWidget displays blank image

Expected behavior
RemoteWidget should handle zero window size and continue rendering process when window size > 0.

Screenshots

Desktop (please complete the following information):

• OS: Windows 10
• Version 0.10.6