Implement a more effective solution for hiding and unhiding columns in ListColumns.

Pros:
- ShowDBProperties doesn't reset column layout
- Sort direction is remembered automatically
- Reading columnlist from registry is done once in a TMDIChild, not on each ShowDBProperties
- Hiding/unhiding columns doesn't call ShowDBProperties
- No more hassling with what is called a "default column" or not. popupDBGrid is usable like in Windows Explorer.
- Column layout is stored global, not per session.
Cons:
- Column layout from old settings logic needed to be discarded

Side effect:
- Fixes a potential AV in FormatNumber(str) with empty strings.
- Created an overloaded FormatByteNumber() which can take a string as input

source/helpers.pas

@@ -81,7 +81,8 @@ type
   function GetFieldValue( Field: TField ): String;
   function LastPos( substr: WideString; str: WideString): Integer;
   function ConvertServerVersion( Version: Integer ): String;
-  function FormatByteNumber( Bytes: Int64; Decimals: Byte = 1 ): String;
+  function FormatByteNumber( Bytes: Int64; Decimals: Byte = 1 ): String; Overload;
+  function FormatByteNumber( Bytes: String; Decimals: Byte = 1 ): String; Overload;
   function FormatTimeNumber( Seconds: Cardinal ): String;
   function TColorToHex( Color : TColor ): string;
   function GetVTCaptions( VT: TVirtualStringTree; OnlySelected: Boolean = False; Column: Integer = 0 ): TStringList;
@@ -1587,7 +1588,10 @@ end;
 }
 function FormatNumber( str: String ): String; Overload;
 begin
-  result := FormatNumber( StrToFloat( str ) );
+  if str <> '' then
+    result := FormatNumber( StrToFloat( str ) )
+  else
+    result := FormatNumber( 0 );
 end;
 
 
@@ -1950,7 +1954,7 @@ end;
   @param Int64 Number of Bytes
   @param Byte Decimals to display when bytes is bigger than 1M
 }
-function FormatByteNumber( Bytes: Int64; Decimals: Byte = 1 ): String;
+function FormatByteNumber( Bytes: Int64; Decimals: Byte = 1 ): String; Overload;
 const
   KB = 1024;
 begin
@@ -1965,6 +1969,16 @@ begin
 end;
 
 
+{**
+  An overloaded function of the previous one which can
+  take a string as input
+}
+function FormatByteNumber( Bytes: String; Decimals: Byte = 1 ): String; Overload;
+begin
+  Result := FormatByteNumber( MakeInt(Bytes), Decimals );
+end;
+
+
 {**
   Format a number of seconds to a human readable time format
   @param Cardinal Number of seconds