Ledger_entry return invalid parameter error for v1 (#873)

Fixes #875

src/rpc/handlers/LedgerEntry.cpp

@@ -82,6 +82,8 @@ LedgerEntryHandler::process(LedgerEntryHandler::Input input, Context const& ctx)
     else
     {
         // Must specify 1 of the following fields to indicate what type
+        if (ctx.apiVersion == 1)
+            return Error{Status{RippledError::rpcINVALID_PARAMS}};
         return Error{Status{ClioError::rpcUNKNOWN_OPTION}};
     }