Guard recursive updates if NNC data import is disabled

Import of NNC data can be turned off in Preferences. If this is off, loading of projects using NNC data can enter a recursive update loop.

ApplicationLibCode/ReservoirDataModel/RigNNCData.cpp

@@ -201,6 +201,9 @@ bool RigNNCData::ensureAllConnectionDataIsProcessed()
 {
     if ( m_haveGeneratedConnections ) return false;
 
+    // Return false if we have no data to process to avoid recursive updates in consuming code
+    if ( !m_mainGrid ) return false;
+
     if ( m_mainGrid )
     {
         caf::ProgressInfo progressInfo( 3, "Computing NNC Data" );