fix: sometimes no staged/unstaged changes were shown (#2030)

Due to a race condition it was possible, that there were changes (the
badge for LOCAL CHANGES showed a non-zero number), but there were no
staged or unstaged files shown.

The problem was, that while loading the changes for the first time, the
watcher could start the loading a second time.  The first loading was
cancelled, but it could have already set the first instance variable. 
Therefore, on the second load a shortcut was done, since there was
seemingly no change.

Author: sina-hide

src/ViewModels/WorkingCopy.cs

@@ -271,8 +271,6 @@ public void SetData(List<Models.Change> changes, CancellationToken cancellationT
                 return;
             }
 
-            _cached = changes;
-
             var lastSelectedUnstaged = new HashSet<string>();
             var lastSelectedStaged = new HashSet<string>();
             if (_selectedUnstaged is { Count: > 0 })
@@ -321,6 +319,7 @@ public void SetData(List<Models.Change> changes, CancellationToken cancellationT
                     return;
 
                 _isLoadingData = true;
+                _cached = changes;
                 HasUnsolvedConflicts = hasConflict;
                 VisibleUnstaged = visibleUnstaged;
                 VisibleStaged = visibleStaged;