fix?: do not block on the main thread when acquiring diff handle

not sure if this will work as I can't reproduce this
but let's see!

helix-vcs/src/diff.rs

@@ -75,6 +75,13 @@ impl DiffHandle {
         }
     }
 
+    pub fn try_load(&self) -> Option<Diff> {
+        Some(Diff {
+            diff: self.diff.try_read()?,
+            inverted: self.inverted,
+        })
+    }
+
     /// Updates the document associated with this redraw handle
     /// This function is only intended to be called from within the rendering loop
     /// if called from elsewhere it may fail to acquire the render lock and panic

helix-view/src/document.rs

@@ -1590,7 +1590,7 @@ impl Document {
                     // file in the file system into what gix::blame knows about (gix::blame only
                     // knows about commit history, it does not know about uncommitted changes)
                     diff_handle
-                        .load()
+                        .try_load()?
                         .hunks_intersecting_line_ranges(std::iter::once((0, cursor_line as usize)))
                         .try_fold(
                             (0, 0),