Origin: upstream, commit:f654f707997610f7de96eeaeadda1ad296034630
Author: Rory McLeod <mcleodnw@gmail.com>
Description: fix #285040 crash when changing a triplet's rest's duration
 - Prevent a null pointer deref when searching a linked tuplet.

--- a/libmscore/edit.cpp
+++ b/libmscore/edit.cpp
@@ -4743,8 +4743,11 @@ void Score::undoAddCR(ChordRest* cr, Mea
                                     if (nt == 0)
                                           qWarning("linked tuplet not found");
                                     }
-                              newcr->setTuplet(nt);
-                              nt->setParent(newcr->measure());
+
+                              if (nt) {
+                                    newcr->setTuplet(nt);
+                                    nt->setParent(newcr->measure());
+                                    }
                               }
                         }