be safe against invalid cond format cell info, fdo#58686

Change-Id: Ie89aee95755d9abd3b82062fac271cfe774174ec
diff --git a/sc/source/ui/view/cellsh1.cxx b/sc/source/ui/view/cellsh1.cxx
index 16e0b06..a805661 100644
--- a/sc/source/ui/view/cellsh1.cxx
+++ b/sc/source/ui/view/cellsh1.cxx
@@ -1792,6 +1792,9 @@ void ScCellShell::ExecuteEdit( SfxRequest& rReq )
                    {
                        // check if at least one existing conditional format has the same range
                        const ScConditionalFormat* pCondFormat = pList->GetFormat(*itr);
                        if(!pCondFormat)
                            continue;

                        const ScRangeList& rCondFormatRange = pCondFormat->GetRange();
                        if(rCondFormatRange == aRangeList)
                        {