Fix bugs causing a crash when histogram is gathered due to uninitilis…

…ed histogram vector

src/core/raster/qgsrasterbandstats.h

@@ -46,6 +46,7 @@ class CORE_EXPORT QgsRasterBandStats
       stdDev = 0.0;
       sum = 0.0;
       elementCount = 0;
+      histogramVector = new HistogramVector();
       isHistogramEstimated = false;
       isHistogramOutOfRange = false;
     }