Fix different document panic (#3160)

Would panic when given the view for the current document for a different document.

helix-view/src/editor.rs

@@ -878,6 +878,7 @@ pub fn switch(&mut self, id: DocumentId, action: Action) {
                 let view = self
                     .tree
                     .try_get(self.tree.focus)
+                    .filter(|v| id == v.doc) // Different Document
                     .cloned()
                     .unwrap_or_else(|| View::new(id, self.config().gutters.clone()));
                 let view_id = self.tree.split(