fix: fix crash when "Save as" is used

Closes #176

src/bpmn-editor.ts

@@ -351,14 +351,10 @@ export class BpmnEditor implements vscode.CustomEditorProvider<BpmnDocument> {
 
     document.onDidDispose(() => disposeAll(listeners));
 
-    // track documents across rename and deletion
+    // track documents
 
     this.documents.add(uri, document);
 
-    document.onDidRename(e => {
-      this.documents.rename(e.oldUri, e.newUri);
-    });
-
     document.onDidDispose(() => this.documents.remove(document.uri));
 
     return document;
@@ -540,18 +536,6 @@ class DocumentCollection {
     return this._documents.delete(key);
   }
 
-  rename(oldUri: vscode.Uri, newUri: vscode.Uri) {
-
-    const document = this.get(oldUri);
-
-    if (!document) {
-      throw new Error('document not found');
-    }
-
-    this.remove(oldUri);
-    this.add(newUri, document);
-  }
-
   add(uri: vscode.Uri, document: BpmnDocument) {
 
     if (this.get(uri)) {