Fix most remaining warnings in satellite .NET projects

ExternalCoreProjects/Virtu/Keyboard.cs

@@ -244,8 +244,10 @@ namespace Jellyfish.Virtu
 			return ret;
 		}
 
+#pragma warning disable CA2211 // public field
 		public static bool WhiteAppleDown;
 		public static bool BlackAppleDown;
+#pragma warning restore CA2211
 
 		/// <summary>
 		/// Call this at 60hz with all of the currently pressed keys

ExternalProjects/PcxFileTypePlugin.HawkQuantizer/OctreeQuantizer.cs

@@ -435,10 +435,7 @@ namespace PcxFileTypePlugin.Quantize
 						// Loop through children looking for leaves
 						for (int index = 0; index < 8; index++)
 						{
-							if (null != _children[index])
-							{
-								_children[index].ConstructPalette(palette, ref paletteIndex);
-							}
+							_children[index]?.ConstructPalette(palette, ref paletteIndex);
 						}
 					}
 				}