Clear diff editor before disposing its TextModels (microsoft#223548)

Author: roblourens

src/vs/workbench/contrib/chat/browser/chatContentParts/chatTextEditContentPart.ts

@@ -75,6 +75,7 @@ export class ChatTextEditContentPart extends Disposable implements IChatContentP
 			this._register(toDisposable(() => {
 				isDisposed = true;
 				cts.dispose(true);
+				this.ref?.object.clearModel();
 			}));
 
 			this.ref = this._register(diffEditorPool.get());

src/vs/workbench/contrib/chat/browser/codeBlockPart.ts

@@ -786,6 +786,10 @@ export class CodeCompareBlockPart extends Disposable {
 			diffEditor: this.diffEditor,
 		} satisfies ICodeCompareBlockActionContext;
 	}
+
+	clearModel() {
+		this.diffEditor.setModel(null);
+	}
 }
 
 export class DefaultChatTextEditor {