fix: improve font string processing in SetFonts method

[gadfly3173]

Fixed the crash when the font is ,SomeFont.

Situation encountered:
When I added Noto Color Emoji, I wrote it at the beginning of the default font. In the TextBox, it was Noto Color Emoji, HarmonyOS Sans SC. Then I found that the digital font became emoji, so I deleted the content before , and the whole app crashed.

[love-linger]

I suggest you to move your code into SourceGit.ViewModels.Preferences.FixFontFamilyName

sourcegit/src/ViewModels/Preferences.cs

Lines 617 to 644 in e3cc987

	private string FixFontFamilyName(string name)
	{
	var trimmed = name.Trim();
	if (string.IsNullOrEmpty(trimmed))
	return string.Empty;
	var builder = new StringBuilder();
	var lastIsSpace = false;
	for (int i = 0; i < trimmed.Length; i++)
	{
	var c = trimmed[i];
	if (char.IsWhiteSpace(c))
	{
	if (lastIsSpace)
	continue;
	lastIsSpace = true;
	}
	else
	{
	lastIsSpace = false;
	}
	builder.Append(c);
	}
	return builder.ToString();
	}

[gadfly3173]

If move code into SourceGit.ViewModels.Preferences.FixFontFamilyName , It would be unable to type , at the end of the font string, I think with the new code, FixFontFamilyName could be removed. Currently, remove the spaces after the font string looks strange.

_sourcegit_20250313150319.mp4

[love-linger]

If we do not remove the whitespace char at the end of a font name, SourceGit will also crashed.

Try Microsoft YaHei , Consolas

[love-linger]

I'll merge this PR first, and add some modifications.

[gadfly3173]

sourcegit/src/App.axaml.cs

Line 453 in 03681ae

var trimmed = part.Trim();

my code trimmed every font