fdo#70143: fix SwDoc::ReplaceRangeImpl() a bit more

Fixes regex replace of "$" with nothing (to delete line
breaks).

Change-Id: If7ec1e5f524f7bb308a2949ace16cb8aa6989106

sw/source/core/doc/docedt.cxx

@@ -2440,18 +2440,23 @@ SetRedlineMode( eOld );
                 }
             }
 
-            if (aDelPam.GetMark() != pStt)
             *rPam.GetPoint() = *aDelPam.GetMark();
-
             ++aPtNd;
             rPam.GetMark()->nNode = aPtNd;
             rPam.GetMark()->nContent.Assign( aPtNd.GetNode().GetCntntNode(),
                                                 nPtCnt );
 
-            if (bJoinTxt && !bJoinPrev)
+            if (bJoinTxt)
             {
+                assert(rPam.GetPoint() == rPam.End());
+                // move so that SetEnd remembers position after sw_JoinText
                 rPam.Move(fnMoveBackward);
             }
+            else if (aDelPam.GetPoint() == pStt) // backward selection?
+            {
+                assert(*rPam.GetMark() <= *rPam.GetPoint());
+                rPam.Exchange(); // swap so that rPam is backwards
+            }
 
             if( pUndoRpl )
             {