Merge pull request #8461 from OPM/8460-plot-curve-fixes

Guard access to QtCharts objects that might be null
Fix visibility of items in legend based on state in parent plot

ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveCollection.cpp

@@ -151,7 +151,7 @@ void RimSummaryCurveCollection::reattachPlotCurves()
 {
     for ( RimSummaryCurve* curve : m_curves )
     {
-        curve->reattach();
+        if ( curve->isCurveVisible() ) curve->reattach();
     }
 }