tdf#120376 sd: fix duplicated styles on copy/paste

Unfortunately the comparison was inverted, so a style is copied
iff it already exists, which is clearly the reviewer's fault...

(regression from 57db6e24b5ad43d447c30e44a112c74c7e75b46b)

Change-Id: I3425982feb08e980eca9243cc16120897b65a70f
Reviewed-on: https://gerrit.libreoffice.org/62436
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
(cherry picked from commit be9f3db2306150a37ef18e4ccc8d8f4a1934c5c1)
Reviewed-on: https://gerrit.libreoffice.org/62449
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>
diff --git a/sd/source/core/stlpool.cxx b/sd/source/core/stlpool.cxx
index 884c9ff..43d6637 100644
--- a/sd/source/core/stlpool.cxx
+++ b/sd/source/core/stlpool.cxx
@@ -652,7 +652,7 @@ void SdStyleSheetPool::CopySheets(SdStyleSheetPool& rSourcePool, SfxStyleFamily 
            pExistingSheet =
                GetStyleSheetByPositionInIndex(aSheetsWithName.front()).get();
            if (!rRenameSuffix.isEmpty() &&
                pExistingSheet->GetItemSet().Equals(xSheet->GetItemSet(), false))
                !pExistingSheet->GetItemSet().Equals(xSheet->GetItemSet(), false))
            {
                // we have found a sheet with the same name, but different contents. Try to find a new name.
                // If we already have a sheet with the new name, and it is equal to the one in the source pool,
@@ -664,7 +664,8 @@ void SdStyleSheetPool::CopySheets(SdStyleSheetPool& rSourcePool, SfxStyleFamily 
                    aTmpName = aName + rRenameSuffix + OUString::number(nSuffix);
                    pExistingSheet = Find(aTmpName, eFamily);
                    nSuffix++;
                } while( pExistingSheet && pExistingSheet->GetItemSet().Equals(xSheet->GetItemSet(), false) );
                } while (pExistingSheet &&
                        !pExistingSheet->GetItemSet().Equals(xSheet->GetItemSet(), false));
                aName = aTmpName;
                bAddToList = true;
            }