skip raster nuller with color types; check data block allocation in block value read, fixes possibly #7807

Author: blazek

src/core/raster/qgsrasterblock.h

@@ -443,6 +443,11 @@ inline void QgsRasterBlock::writeValue( void *data, QGis::DataType type, size_t
 
 inline double QgsRasterBlock::value( size_t index ) const
 {
+  if ( !mData )
+  {
+    QgsDebugMsg( "Data block not allocated" );
+    return std::numeric_limits<double>::quiet_NaN();
+  }
   return readValue( mData, mDataType, index );
 }
 

src/core/raster/qgsrasternuller.cpp

@@ -74,11 +74,21 @@ QgsRasterBlock * QgsRasterNuller::block( int bandNo, QgsRectangle  const & exten
   QgsDebugMsg( "Entered" );
   if ( !mInput )
   {
-    QgsRasterBlock *outputBlock = new QgsRasterBlock();
-    return outputBlock;
+    return new QgsRasterBlock();
   }
 
   QgsRasterBlock *inputBlock = mInput->block( bandNo, extent, width, height );
+  if ( !inputBlock )
+  {
+    return new QgsRasterBlock();
+  }
+
+  // We don't support nuller for color types
+  if ( QgsRasterBlock::typeIsColor( inputBlock->dataType() ) )
+  {
+    return inputBlock;
+  }
+
   QgsRasterBlock *outputBlock = 0;
 
   if ( mHasOutputNoData.value( bandNo - 1 ) || inputBlock->hasNoDataValue() )