nullptr check added

src/nodes/QskSGNode.cpp

@@ -87,6 +87,8 @@ void QskSGNode::setParentNode( QSGNode* node, QSGNode* parent )
 }
 
 QSGNode* QskSGNode::findChildNode( QSGNode* parent, quint8 role )
+{
+    if ( parent )
     {
         auto node = parent->firstChild();
         while ( node )
@@ -96,6 +98,7 @@ QSGNode* QskSGNode::findChildNode( QSGNode* parent, quint8 role )
 
             node = node->nextSibling();
         }
+    }
 
     return nullptr;
 }