fix(windows): check font count display none found

This change is to check number of fonts found for keyboard
to guard against trying to index it when there are no fonts.
  for i := 0 to grid.RowCount - 1 do
        m := System.Math.Max(m,
	Canvas.TextWidth(FSelectedKeyboard.Fonts[i].FontName) + 6)
It also notifies the user no suggested fonts where found.

windows/src/desktop/kmshell/xml/strings.xml

@@ -1186,7 +1186,10 @@ keyboard that you use in Windows.  Keyman keyboards will adapt automatically to
   <!-- Introduced: 8.0.294.0 -->
   <string name="S_OSK_FontHelper_ChooseKeyboard" comment="OSK Font helper choose keyboard">Please select a Keyman keyboard to find related fonts.</string>
 
-
+  <!-- Context: OSK Font Helper -->
+  <!-- String Type: FormatString -->
+  <!-- Introduced: 17.0.312.0 -->
+  <string name="S_OSK_FontHelper_NoFonts" comment="OSK Font helper no fonts found for keyboard">No fonts have been found as suggestions for Keyboard %1$s .</string>
 
   <!-- Context: Text Editor -->
   <!-- String Type: FormatString -->

windows/src/engine/keyman/viskbd/UfrmOSKFontHelper.pas

@@ -1,18 +1,18 @@
 (*
   Name:             UfrmOSKFontHelper
   Copyright:        Copyright (C) SIL International.
-  Documentation:    
-  Description:      
+  Documentation:
+  Description:
   Create Date:      27 Mar 2008
 
   Modified Date:    25 Sep 2014
   Authors:          mcdurdin
-  Related Files:    
-  Dependencies:     
+  Related Files:
+  Dependencies:
 
-  Bugs:             
-  Todo:             
-  Notes:            
+  Bugs:
+  Todo:
+  Notes:
   History:          27 Mar 2008 - mcdurdin - Initial version I1374
                     20 Jul 2008 - mcdurdin - I1533 - Show hint for non-Unicode keyboards
                     29 Mar 2010 - mcdurdin - I2199 - Shift+click
@@ -447,39 +447,47 @@ procedure TfrmOSKFontHelper.DisplayKeyboardFonts;
   FKeyboard := FCheckFontKeyboards.Keyboards[FLastSelectedKeyboardID];
   if (FLastSelectedKeyboardID <> '') and Assigned(FKeyboard) then
   begin
-    SetLength(FChars, Length(FKeyboard.Chars));
-    J := 0;
-    I := 1;
-    while I <= Length(FKeyboard.Chars) do  // I2712
+    if FKeyboard.Fonts.Count > 0 then
     begin
-      ch := FKeyboard.Chars[I];
-      if Uni_IsSurrogate1(ch) and (I < Length(FKeyboard.Chars)) and Uni_IsSurrogate2(FKeyboard.Chars[I+1]) then
+      SetLength(FChars, Length(FKeyboard.Chars));
+      J := 0;
+      I := 1;
+      while I <= Length(FKeyboard.Chars) do  // I2712
       begin
-        ch2 := FKeyboard.Chars[I+1];
-        FChars[J] := Uni_SurrogateToUTF32(ch, ch2);
+        ch := FKeyboard.Chars[I];
+        if Uni_IsSurrogate1(ch) and (I < Length(FKeyboard.Chars)) and Uni_IsSurrogate2(FKeyboard.Chars[I+1]) then
+        begin
+          ch2 := FKeyboard.Chars[I+1];
+          FChars[J] := Uni_SurrogateToUTF32(ch, ch2);
+          Inc(I);
+        end
+        else
+          FChars[J] := Ord(ch);
         Inc(I);
-      end
-      else
-        FChars[J] := Ord(ch);
-      Inc(I);
-      Inc(J);
-    end;
+        Inc(J);
+      end;
 
-    SetLength(FChars, J);
+      SetLength(FChars, J);
 
-    grid.ColCount := Length(FChars) + 2;
-    grid.RowCount := FKeyboard.Fonts.Count;
+      grid.ColCount := Length(FChars) + 2;
+      grid.RowCount := FKeyboard.Fonts.Count;
 
-    for i := 0 to FKeyboard.Fonts.Count - 1 do
-      if FKeyboard.Fonts[i].Coverage < 50 then
-      begin
-        grid.RowCount := i;
-        Break;
-      end;
+      for i := 0 to FKeyboard.Fonts.Count - 1 do
+        if FKeyboard.Fonts[i].Coverage < 50 then
+        begin
+          grid.RowCount := i;
+          Break;
+        end;
 
-    FSelectedKeyboard := FKeyboard;
-    FormatGrid;
-    SetDisplay('');
+      FSelectedKeyboard := FKeyboard;
+      FormatGrid;
+      SetDisplay('');
+    end
+    else
+    begin
+       FSelectedKeyboard := FKeyboard;
+       SetDisplay(MsgFromIdFormat(S_OSK_FontHelper_NoFonts, [FSelectedKeyboard.Name]));
+    end;
   end
   else
   begin