coverity#1267681 Dereference before null check

Change-Id: I629b12d53ef3bbadeb43e9555a8499252c1a1800

include/vcl/bmpacc.hxx

@@ -348,14 +348,14 @@ inline Scanline BitmapReadAccess::GetBuffer() const
 
 inline Scanline BitmapReadAccess::GetScanline( long nY ) const
 {
-    assert(mpBuffer && "Access is not valid!");
+    assert(mpBuffer && mpScanBuf && "Access is not valid!");
     assert(nY < mpBuffer->mnHeight && "y-coordinate out of range!");
-    return( mpBuffer ? mpScanBuf[ nY ] : NULL );
+    return mpScanBuf[nY];
 }
 
 inline BitmapColor BitmapReadAccess::GetPixel( long nY, long nX ) const
 {
-    assert(mpBuffer && "Access is not valid!");
+    assert(mpBuffer && mpScanBuf && "Access is not valid!");
     assert(nX < mpBuffer->mnWidth && "x-coordinate out of range!");
     assert(nY < mpBuffer->mnHeight && "y-coordinate out of range!");
     return mFncGetPixel( mpScanBuf[ nY ], nX, maColorMask );

vcl/source/gdi/bmpacc.cxx

@@ -426,7 +426,7 @@ BitmapWriteAccess::~BitmapWriteAccess()
 
 void BitmapWriteAccess::CopyScanline( long nY, const BitmapReadAccess& rReadAcc )
 {
-    DBG_ASSERT( ( nY >= 0 ) && ( nY < mpBuffer->mnHeight ), "y-coordinate in destination out of range!" );
+    assert(nY >= 0 && nY < mpBuffer->mnHeight && "y-coordinate in destination out of range!");
     DBG_ASSERT( nY < rReadAcc.Height(), "y-coordinate in source out of range!" );
     DBG_ASSERT( ( HasPalette() && rReadAcc.HasPalette() ) || ( !HasPalette() && !rReadAcc.HasPalette() ), "No copying possible between palette bitmap and TC bitmap!" );
 
@@ -446,7 +446,7 @@ void BitmapWriteAccess::CopyScanline( long nY, ConstScanline aSrcScanline,
 {
     const sal_uLong nFormat = BMP_SCANLINE_FORMAT( nSrcScanlineFormat );
 
-    DBG_ASSERT( ( nY >= 0 ) && ( nY < mpBuffer->mnHeight ), "y-coordinate in destination out of range!" );
+    assert(nY >= 0 && nY < mpBuffer->mnHeight && "y-coordinate in destination out of range!");
     DBG_ASSERT( ( HasPalette() && nFormat <= BMP_FORMAT_8BIT_PAL ) ||
                 ( !HasPalette() && nFormat > BMP_FORMAT_8BIT_PAL ),
                 "No copying possible between palette and non palette scanlines!" );