fixes #15878

src/vs/workbench/parts/git/common/gitContentProvider.ts

@@ -44,7 +44,7 @@ export class GitContentProvider implements IWorkbenchContribution, ITextModelCon
 		const treeish = gitModel.getStatus().find(path, StatusType.INDEX) ? '~' : 'HEAD';
 
 		return this.gitService.buffer(path, treeish)
-			.then(contents => this.modelService.createModel(contents, null, uri))
+			.then(contents => this.modelService.createModel(contents || '', null, uri))
 			.then(model => {
 				const trigger = () => {
 					this.throttler.queue(() => {

src/vs/workbench/parts/scm/browser/dirtydiffDecorator.ts

@@ -114,12 +114,13 @@ class DirtyDiffModelDecorator {
 	}
 
 	private diff(): winjs.Promise {
-		if (!this.model || this.model.isDisposed()) {
-			return winjs.TPromise.as<any>([]); // disposed
-		}
+		return this.originalURIPromise.then(originalURI => {
+			if (!this.model || this.model.isDisposed()) {
+				return winjs.TPromise.as<any>([]); // disposed
+			}
 
-		return this.originalURIPromise
-			.then(originalURI => this.editorWorkerService.computeDirtyDiff(originalURI, this.model.uri, true));
+			this.editorWorkerService.computeDirtyDiff(originalURI, this.model.uri, true);
+		});
 	}
 
 	private static changesToDecorations(diff: common.IChange[]): common.IModelDeltaDecoration[] {