guard against corrupt SilverBullet

Change-Id: I3af47ab3af5e28a865a77a592f6a92edb46e4f2b
(cherry picked from commit 36d55980)
Reviewed-on: https://gerrit.libreoffice.org/20504Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

lotuswordpro/source/filter/lwpsilverbullet.cxx

@@ -94,6 +94,9 @@ void LwpSilverBullet::Read()
 
     sal_uInt16 nNumPos = m_pObjStrm->QuickReaduInt16();
 
+    if (nNumPos > SAL_N_ELEMENTS(m_pResetPositionFlags))
+        throw std::range_error("corrupt SilverBullet");
+
     for (sal_uInt16 nC = 0; nC < nNumPos; nC++)
         m_pResetPositionFlags[nC] = m_pObjStrm->QuickReaduInt8();