[Lazarus] TStringGrid sort symbol in TitleButton

[Landmesser John]

In a StringGrid without(!) defined columns you never see that up and 
down arrow in the TitleButton if you click to sort this column.

It's ok if you define at least one column, but i think that shouldn't be 
this way.

Attached patch comments out

//FImageIndex := -1;

My first patch :-)

Lazarus 1.9.0 r57932M FPC 3.0.4 i386-win32-win32/win64

-------------- next part --------------
Index: lcl/grids.pas
===================================================================
--- lcl/grids.pas	(Revision 57932)
+++ lcl/grids.pas	(Arbeitskopie)
@@ -11858,7 +11858,7 @@
   FFont := TFont.Create;
   FillTitleDefaultFont;
   FFont.OnChange := @FontChanged;
-  FImageIndex := -1;
+  //FImageIndex := -1;
   FImageLayout := blGlyphRight;
   FIsDefaultCaption := true;
 end;