created function that splits and preserves links

app/node/block/block.cpp

@@ -235,6 +235,10 @@ void Block::Link(Block *a, Block *b)
     return;
   }
 
+  if (a == nullptr || b == nullptr) {
+    return;
+  }
+
   // Assume both clips are already linked since Link() and Unlink() should be the only entry points to this array
   if (a->linked_clips_.contains(b)) {
     return;
@@ -259,6 +263,11 @@ void Block::Unlink(Block *a, Block *b)
   b->linked_clips_.removeOne(a);
 }
 
+bool Block::AreLinked(Block *a, Block *b)
+{
+  return a->linked_clips_.contains(b);
+}
+
 const QVector<Block*> &Block::linked_clips()
 {
   return linked_clips_;