Cannot delete values with hook_param_set.

[tequdev]

chook test

xahaud/src/test/app/SetHook_test.cpp

Line 5804 in eec61f1

ASSERT(hook_param_set(0,0,"checker", 7, SBUF(checker_hash)) == 0);

jshooks implementation

xahaud/src/ripple/app/hook/impl/applyHook.cpp

Lines 8866 to 8870 in eec61f1

	if (!param_key.has_value() || param_key->empty() ||
	param_key->size() > hook::maxHookParameterKeySize() ||
	!param_val.has_value() || param_val->size() > hook::maxHookParameterValueSize() ||
	!param_hash.has_value() || param_hash->size() != 32)
	returnJS(INVALID_ARGUMENT);

param_key should be allowed to be null/undefined.