prevent invalid size instructions since apparently that can happen

CollabVMSharp/CollabVMClient.cs

@@ -292,6 +292,7 @@ public class CollabVMClient {
                 if (msgArr[1] != "0") return;
                 var width = int.Parse(msgArr[2]);
                 var height = int.Parse(msgArr[3]);
+                if (width == 0 || height == 0) return;
                 this.framebuffer = new Image<Rgba32>(width, height);
                 this.ScreenSize.Invoke(this, new ScreenSizeEventArgs { Width = width, Height = height });
                 break;