Fix possible crash when looking for version control for directory

Task-number: QTCREATORBUG-9656

Change-Id: If8babdb942830bd11fe360a311c57b75312248be
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>

src/plugins/coreplugin/vcsmanager.cpp

@@ -287,8 +287,8 @@ IVersionControl* VcsManager::findVersionControlForDirectory(const QString &input
             }
             return versionControl;
         } else {
-            InfoBar *infoBar = curDocument->infoBar();
-            if (infoBar->canInfoBeAdded(vcsWarning)) {
+            InfoBar *infoBar = curDocument ? curDocument->infoBar() : 0;
+            if (infoBar && infoBar->canInfoBeAdded(vcsWarning)) {
                 InfoBarEntry info(vcsWarning,
                                   tr("%1 repository was detected but %1 is not configured.")
                                   .arg(versionControl->displayName()),