Protect against NULL User/Group comment when removing comment

Fixes 8941 (hopefully)

Author: robmen

src/ext/Util/ca/scaexec.cpp

@@ -764,6 +764,7 @@ extern "C" UINT __stdcall CreateUser(
     WCA_CASCRIPT_HANDLE hRollbackScript = NULL;
     int iOriginalAttributes = 0;
     int iRollbackAttributes = 0;
+    LPCWSTR wzOriginalComment = NULL;
 
     USER_INFO_1 userInfo1;
     USER_INFO_1* pUserInfo1 = NULL;
@@ -885,14 +886,16 @@ extern "C" UINT __stdcall CreateUser(
                                 }
                             }
 
-                            hr = WcaCaScriptWriteString(hRollbackScript, pUserInfo1->usri1_comment);
-                            ExitOnFailure(hr, "Failed to add rollback comment to rollback script.");
-
-                            if (!pUserInfo1->usri1_comment || !*pUserInfo1->usri1_comment)
+                            wzOriginalComment = pUserInfo1->usri1_comment;
+                            if (!wzOriginalComment || !*wzOriginalComment)
                             {
                                 iRollbackAttributes |= SCAU_REMOVE_COMMENT;
+                                wzOriginalComment = L"";
                             }
 
+                            hr = WcaCaScriptWriteString(hRollbackScript, wzOriginalComment);
+                            ExitOnFailure(hr, "Failed to add rollback comment to rollback script.");
+
                             hr = WcaCaScriptWriteNumber(hRollbackScript, iRollbackAttributes);
                             ExitOnFailure(hr, "Failed to add rollback attributes to rollback script.");
 
@@ -1247,6 +1250,7 @@ extern "C" UINT __stdcall CreateGroup(
 
     WCA_CASCRIPT_HANDLE hRollbackScript = NULL;
     int iRollbackAttributes = 0;
+    LPCWSTR wzOriginalComment = NULL;
 
     DWORD dw;
     LPWSTR pwzServerName = NULL;
@@ -1338,14 +1342,16 @@ extern "C" UINT __stdcall CreateGroup(
 
                             iRollbackAttributes = 0;
 
-                            hr = WcaCaScriptWriteString(hRollbackScript, pGroupInfo1->lgrpi1_comment);
-                            ExitOnFailure(hr, "Failed to add rollback comment to rollback script.");
-
-                            if (!pGroupInfo1->lgrpi1_comment || !*pGroupInfo1->lgrpi1_comment)
+                            wzOriginalComment = pGroupInfo1->lgrpi1_comment;
+                            if (!wzOriginalComment || !*wzOriginalComment)
                             {
                                 iRollbackAttributes |= SCAG_REMOVE_COMMENT;
+                                wzOriginalComment = L"";
                             }
 
+                            hr = WcaCaScriptWriteString(hRollbackScript, wzOriginalComment);
+                            ExitOnFailure(hr, "Failed to add rollback comment to rollback script.");
+
                             hr = WcaCaScriptWriteNumber(hRollbackScript, iRollbackAttributes);
                             ExitOnFailure(hr, "Failed to add rollback attributes to rollback script.");
 

src/test/msi/WixToolsetTest.MsiE2E/UtilExtensionGroupTests.cs

@@ -243,7 +243,7 @@ public void CanRepairCommentOfNewNonDomainGroup()
         }
 
         // Verify that a comment can be changed for an existing group
-        [RuntimeFact(Skip = "wixtoolset/issues#8941 - This test fails intermittently in CI. Disabling until the root cause is fixed.")]
+        [RuntimeFact]
         public void CanChangeCommentOfExistingNonDomainGroup()
         {
             try