CID#1079343 mContext.cipher is not initialized...

use protected to indicate that this is not callable directly, but only by
another ctor which will do the initialization. Not sure if coverity will grok
that, but if it doesn't then it can be submitted as a false positive

Change-Id: I8e97c0b441dc407a005913e2b10f0fb48f45672b

include/oox/crypto/CryptTools.hxx

@@ -72,9 +72,10 @@ protected:
             CK_ATTRIBUTE_TYPE operation);
 #endif
 
-public:
+protected:
     Crypto(CryptoType type);
 
+public:
     virtual ~Crypto();
 
     virtual sal_uInt32 update(