fix LS_COLORS fi=0 coloring (#16012)

# Description

fixes #16010

When `$env.LS_COLORS = 'fi=0' and `$env.config.color_config.string =
'red'` were set, regular files without file extensions would be colored
red. Now they're colored based on the LS_COLORS definition which, in
this case, means use default colors.

This is done by checking if a style was applied from ls_colors and if
none was applied, create a default nu_ansi_term style with
'Color::Default' for foreground and background.

### Before

![image](https://github.com/user-attachments/assets/ff245ee9-3299-4362-9df7-95613e8972ed)

### After

![image](https://github.com/user-attachments/assets/7c3f1178-6e6b-446d-b88c-1a5b0747345d)



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---------

Co-authored-by: Bahex <Bahex@users.noreply.github.com>

crates/nu-command/src/viewers/table.rs

@@ -1056,7 +1056,28 @@ fn render_path_name(
         && has_metadata
         && config.shell_integration.osc8;
 
-    let ansi_style = style.map(Style::to_nu_ansi_term_style).unwrap_or_default();
+    // If there is no style at all set it to use 'default' foreground and background
+    // colors. This prevents it being colored in tabled as string colors.
+    // To test this:
+    //   $env.LS_COLORS = 'fi=0'
+    //   $env.config.color_config.string = 'red'
+    // if a regular file without an extension is the color 'default' then it's working
+    // if a regular file without an extension is the color 'red' then it's not working
+    let ansi_style = style
+        .map(Style::to_nu_ansi_term_style)
+        .unwrap_or(nu_ansi_term::Style {
+            foreground: Some(nu_ansi_term::Color::Default),
+            background: Some(nu_ansi_term::Color::Default),
+            is_bold: false,
+            is_dimmed: false,
+            is_italic: false,
+            is_underline: false,
+            is_blink: false,
+            is_reverse: false,
+            is_hidden: false,
+            is_strikethrough: false,
+            prefix_with_reset: false,
+        });
 
     let full_path = PathBuf::from(stripped_path.as_ref())
         .canonicalize()