Fix incorrect count in DrawMeshInstanced

The last Graphics.DrawMeshInstanced call is supposed to only render
stragglers that don't fit in full batches. However, instead it 
renders 1023 elements, rendering extra elements that shouldn't be there.
This mistake was probably due to a copy and paste error.

Fixed by introducing a stragglerCount to avoid calling % twice 
and to give better clarity.

Assets/_Scripts/GraphicsSystem.cs

-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -89,10 +89,11 @@ public class GraphicsSystem
                                            ShadowCastingMode.Off, false);
             }
 
-            NativeArray<float4x4>.Copy(mTransformMatrices, range.start + i * 1023, mMatrixBufferAsNativeArray, 0, range.length % 1023);
+            var stragglerCount = range.length % 1023;
+            NativeArray<float4x4>.Copy(mTransformMatrices, range.start + i * 1023, mMatrixBufferAsNativeArray, 0, stragglerCount);
             Graphics.DrawMeshInstanced(mesh, 0,
                                        material, mMatrixBuffer,
-                                       1023, null,
+                                       stragglerCount, null,
                                        ShadowCastingMode.Off, false);
 
         }