Fix testing pathRepository for null (#1304)

Author: fcollonval

src/commandsAndMenu.tsx

@@ -1276,7 +1276,7 @@ export function addCommands(
     ),
     execute: async args => {
       const { files } = args as any as CommandArguments.IGitFileDiff;
-      if (!gitModel.pathRepository) {
+      if (gitModel.pathRepository === null) {
         return;
       }
 

src/model.ts

@@ -360,7 +360,7 @@ export class GitExtension implements IGitExtension {
    * Note: This makes sure it always returns non null value
    */
   protected get _currentMarker(): BranchMarker {
-    if (!this.pathRepository) {
+    if (this.pathRepository === null) {
       return new BranchMarker(() => {});
     }