anchor.diff:  					// init diagram toolbar
   					mainView.initToolbar(diagram, gene);
   
  -					if (self.mut3dVisView)
  +					if (self.mut3dVisView &&
  +						pdbData)
   					{
  +						// collection of pdb model instances
  +						var pdbColl = self.util.processPdbData(gene, pdbData);
  +
   						// init the 3d view
   						var view3d = new Mutation3dView({
   							el: "#mutation_3d_" + gene,
  
positive.code: 
  			// callback function to init view after retrieving
  			// sequence information.
  			var init = function(sequence, pdbData)
  			{
  				// collection of pdb model instances
  				var pdbColl = self.util.processPdbData(gene, pdbData);
  				// calculate somatic & germline mutation rates
  				var mutationCount = self.util.countMutations(gene, cases);
  				// generate summary string for the calculated mutation count values
  
negative.code: 					positions: positionData.join(" ")},
  					function(pdbData) {
  						// init view with the sequence and pdb data
  						init(sequenceData, pdbData);
  				});
  			};
  
  			// get sequence data & pdb data for the current gene & init view
  			if (self.options.mut3dVis)
  			{
  				$.getJSON("getPfamSequence.json", {geneSymbol: gene}, getPdbData);
  			}
  			else
  			{
  				// if no 3D visualizer is available, just skip pdb data retrieval
  				$.getJSON("getPfamSequence.json", {geneSymbol: gene}, init);
  			}
  		},
  		/**
  		 * Initializes the mutation diagram view.
  