final check np bounds

Change-Id: I9213bb2cc059e05e286598edac03bd72c84db876
(cherry picked from commit dcbbe774)
Reviewed-on: https://gerrit.libreoffice.org/17212Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

filter/source/graphicfilter/itiff/itiff.cxx

@@ -551,6 +551,8 @@ bool TIFFReader::ReadMap()
                 if ( nStrip >= nNumStripOffsets )
                     return false;
                 pTIFF->Seek( pStripOffsets[ nStrip ] + ( ny % GetRowsPerStrip() ) * nStripBytesPerRow );
+                if (np >= SAL_N_ELEMENTS(pMap))
+                    return false;
                 pTIFF->Read( pMap[ np ], nBytesPerRow );
                 if ( pTIFF->GetError() )
                     return false;