Fix #306917: Crash on tie in score with parts

Resolves: https://musescore.org/en/node/306917.

Apply the same method from https:://github.com//pull/6049 in undoAddElement() for determining the tracks in which to place new elements.

libmscore/edit.cpp

@@ -4532,17 +4532,48 @@ void Score::undoAddElement(Element* element)
             return;
             }
 
+      // For linked staves the length of staffList is always > 1 since the list contains the staff itself too!
+      const bool linked = ostaff->staffList().length() > 1;
+
       for (Staff* staff : ostaff->staffList()) {
             Score* score = staff->score();
             int staffIdx = staff->idx();
 
             QList<int> tr;
-            if ((strack & ~3) != staffIdx) // linked staff ?
-                  tr.append(staffIdx * VOICES + (strack % VOICES));
-            else if (staff->score()->excerpt() && strack > -1)
-                  tr = staff->score()->excerpt()->tracks().values(strack);
-            else
-                  tr.append(strack);
+            if (!staff->score()->excerpt()) {
+                  // On masterScore.
+                  int track = staff->idx() * VOICES + (strack % VOICES);
+                  tr.append(track);
+                  }
+            else {
+                  QMultiMap<int, int> mapping = staff->score()->excerpt()->tracks();
+                  if (mapping.isEmpty()) {
+                        // This can happen during reading the score and there is
+                        // no Tracklist tag specified.
+                        // TODO solve this in read301.cpp.
+                        tr.append(strack);
+                        }
+                  else {
+                        for (int track : mapping.values(strack)) {
+                              // linkedPart : linked staves within same part/instrument.
+                              // linkedScore: linked staves over different scores via excerpts.
+                              const bool linkedPart  = linked && (staff != ostaff) && (staff->score() == ostaff->score());
+                              const bool linkedScore = linked && (staff != ostaff) && (staff->score() != ostaff->score());
+                              if (linkedPart && !linkedScore) {
+                                    tr.append(staff->idx() * VOICES + mapping.value(track));
+                                    }
+                              else if (!linkedPart && linkedScore) {
+                                    if ((track >> 2) != staffIdx)
+                                          track += (staffIdx - (track >> 2)) * VOICES;
+                                    tr.append(track);
+                                    }
+                              else {
+                                    tr.append(track);
+                                    }
+                              }
+                        }
+                  }
+
 
             // Some elements in voice 1 of a staff should be copied to every track which has a linked voice in this staff
 
@@ -4565,13 +4596,7 @@ void Score::undoAddElement(Element* element)
                   tr.append(staffIdx * VOICES);
                   }
 
-            int it = 0;
             for (int ntrack : tr) {
-                  if ((ntrack & ~3) != staffIdx * VOICES) {
-                        it++;
-                        continue;
-                        }
-
                   Element* ne;
                   if (staff == ostaff)
                         ne = element;
@@ -4880,7 +4905,6 @@ void Score::undoAddElement(Element* element)
                         }
                   else
                         qWarning("undoAddElement: unhandled: <%s>", element->name());
-                  it++;
                   }
             }
       }