Fix computing intensity features over spots that are only made of NaNs.

For spots that contained only NaNs, the 'intensities' array was empty
and the edited lines generated a NPE.

Author: tinevez

src/main/java/fiji/plugin/trackmate/features/spot/SpotIntensityMultiCAnalyzer.java

@@ -65,12 +65,36 @@ public void process( final Spot spot )
 			intensities.addValue( val );
 		}
 
-		Util.quicksort( intensities.getArray(), 0, intensities.size() - 1 );
-		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MEAN_INTENSITY, channel ), Double.valueOf( TMUtils.average( intensities ) ) );
-		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MEDIAN_INTENSITY, channel ), Double.valueOf( intensities.getArray()[ intensities.size() / 2 ] ) );
-		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MIN_INTENSITY, channel ), Double.valueOf( intensities.getArray()[ 0 ] ) );
-		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MAX_INTENSITY, channel ), Double.valueOf( intensities.getArray()[ intensities.size() - 1 ] ) );
-		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( TOTAL_INTENSITY, channel ), Double.valueOf( TMUtils.sum( intensities ) ) );
-		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( STD_INTENSITY, channel ), Double.valueOf( TMUtils.standardDeviation( intensities ) ) );
+		final double mean;
+		final double median;
+		final double max;
+		final double min;
+		final double sum;
+		final double std;
+		if ( intensities.isEmpty() )
+		{
+			mean = Double.NaN;
+			median = Double.NaN;
+			max = Double.NaN;
+			min = Double.NaN;
+			sum = Double.NaN;
+			std = Double.NaN;
+		}
+		else
+		{
+			Util.quicksort( intensities.getArray(), 0, intensities.size() - 1 );
+			mean = Double.valueOf( TMUtils.average( intensities ) );
+			median = Double.valueOf( intensities.getArray()[ intensities.size() / 2 ] );
+			min = Double.valueOf( intensities.getArray()[ 0 ] );
+			max = Double.valueOf( intensities.getArray()[ intensities.size() - 1 ] );
+			sum = Double.valueOf( TMUtils.sum( intensities ) );
+			std = Double.valueOf( TMUtils.standardDeviation( intensities ) );
+		}
+		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MEAN_INTENSITY, channel ), mean );
+		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MEDIAN_INTENSITY, channel ), median );
+		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MIN_INTENSITY, channel ), min );
+		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( MAX_INTENSITY, channel ), max );
+		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( TOTAL_INTENSITY, channel ), sum );
+		spot.putFeature( SpotIntensityMultiCAnalyzerFactory.makeFeatureKey( STD_INTENSITY, channel ), std );
 	}
 }