win32: fixed alloc draw buffer

demo/ButtonGenerator/ButtonGenerator.lpr

@@ -2,6 +2,10 @@ program ButtonGenerator;
 
 {$mode objfpc}{$H+}
 
+{$IFDEF Windows}
+  {$AppType Console}
+{$ENDIF}
+
 uses
   {$IFDEF UNIX}
   cthreads,

src/win32/fresnel.win32.pas

@@ -119,7 +119,7 @@ begin
   aStride:=aWidth*4;
   aBuffer:=0;
   aData:=nil;
-  aBitmapInfo:=AllocMem(SizeOf(TBITMAPINFOHEADER));
+  aBitmapInfo:=AllocMem(SizeOf(TBITMAPINFOHEADER)+SizeOf(ColorMasks));
   try
     with aBitmapInfo^.bmiHeader do
     begin