Test IsPushOnly() with invalid push

src/script.cpp

@@ -1874,9 +1874,11 @@ bool CScript::IsPushOnly() const
     const_iterator pc = begin();
     while (pc < end())
     {
+        // Note how a script with an invalid PUSHDATA returns False.
         opcodetype opcode;
         if (!GetOp(pc, opcode))
             return false;
+
         // Note that IsPushOnly() *does* consider OP_RESERVED to be a
         // push-type opcode, however execution of OP_RESERVED fails, so
         // it's not relevant to P2SH as the scriptSig would fail prior to