From ef5e419012d2a4966d0d5eea7513262a37a8b671 Mon Sep 17 00:00:00 2001
From: Anton Makeev <Anton.Makeev@jetbrains.com>
Date: Thu, 23 Aug 2012 10:52:56 +0200
Subject: [PATCH] Platform: Cannot Undo... dialog references some not-existing
 Dummy.txt file (OC-4896) (cherry picked from commit
 7e3db0cf4eaf79bc88e748848fe4e25e8d595035)

---
 .../com/intellij/openapi/command/impl/CommandMerger.java   | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/platform/platform-impl/src/com/intellij/openapi/command/impl/CommandMerger.java b/platform/platform-impl/src/com/intellij/openapi/command/impl/CommandMerger.java
index ca9103d60b1a..cdd3b27502ef 100644
--- a/platform/platform-impl/src/com/intellij/openapi/command/impl/CommandMerger.java
+++ b/platform/platform-impl/src/com/intellij/openapi/command/impl/CommandMerger.java
@@ -185,11 +185,12 @@ public class CommandMerger {
   }
 
   private boolean affectsMultiplePhysicalDocs() {
-    int count = 0;
+    Set<VirtualFile> affectedFiles = new HashSet<VirtualFile>();
     for (DocumentReference each : myAllAffectedDocuments) {
       VirtualFile file = each.getFile();
-      if (file instanceof LightVirtualFile) continue;
-      if (++count > 1) return true;
+      if (file == null || file instanceof LightVirtualFile) continue;
+      affectedFiles.add(file);
+      if (affectedFiles.size() > 1) return true;
     }
     return false;
   }