Improve charting UI for error cases

Web/Controllers/ChartController.cs

@@ -4,6 +4,7 @@ using System.Drawing;
 using System.Drawing.Imaging;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Web.Mvc;
 using System.Web.UI.DataVisualization.Charting;
 using System.Web.UI.WebControls;
@@ -57,7 +58,7 @@ namespace LeafWeb.Web.Controllers
 		    var curveData = GetCurveData(leafOutputFile.FileContents.Contents, curveId);
 
 		    if (curveData == null)
-			    return File("/Content/favicon/apple-icon-57x57.png", "image/png"); // TODO: different image ?
+			    return new HttpStatusCodeResult(HttpStatusCode.NotFound);
 
 		    var charts = GetChartBitmaps(curveData).ToList();
 
@@ -75,11 +76,18 @@ namespace LeafWeb.Web.Controllers
 
 		private CurveData GetCurveData(byte[] fileContents, string curveId)
 		{
-			LeafGasComparison[] leafGasComparisons;
-			using (var parser = new LeafGasComparisonParser(fileContents))
-				leafGasComparisons = parser.Parse(curveId);
-
-			return CurveDataConverter.Convert(leafGasComparisons).First();
+			try
+			{
+				LeafGasComparison[] leafGasComparisons;
+				using (var parser = new LeafGasComparisonParser(fileContents))
+					leafGasComparisons = parser.Parse(curveId);
+				return CurveDataConverter.Convert(leafGasComparisons).First();
+			}
+			catch (Exception e)
+			{
+				LogManager.GetCurrentClassLogger().Warn(e);
+			}
+			return null;
 		}
 
 		private string[] GetCurveIds(byte[] fileContents)