fix: handle file mtime overflow (#1959)

Modification time is doing an unchecked add. Files with bad mtime will
overflow and crash the app.

Use a checked add instead, returning None and displaying an empty mtime
instead.

This only affects mtimes via GVFS. Viewing local files works because it
interprets the mtime directly instead of relying on addition.

Fixes #1886 

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src/tab.rs

@@ -437,7 +437,9 @@ impl<'a> FormatTime<'a> {
 
 impl Display for FormatTime<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let zoned = jiff::Zoned::try_from(self.time).unwrap();
+        let Ok(zoned) = jiff::Zoned::try_from(self.time) else {
+            return Ok(());
+        };
         let now = jiff::Zoned::now();
         let icu_datetime = DateTime::convert_from(zoned.datetime());
         if zoned.date() == now.date() {
@@ -1909,7 +1911,7 @@ impl ItemMetadata {
             Self::Path { metadata, .. } => metadata.modified().ok(),
             #[cfg(feature = "gvfs")]
             Self::GvfsPath { mtime, .. } => {
-                Some(SystemTime::UNIX_EPOCH + Duration::from_secs(*mtime))
+                SystemTime::UNIX_EPOCH.checked_add(Duration::from_secs(*mtime))
             }
             _ => None,
         }