Deletion of decimals fail with a 409

[Vinnl]

When I write the following data to my Pod:

@prefix : <#>.
@prefix schem: <http://schema.org/>.

:160581889284507796464006133086
a schem:MonetaryAmount; schem:amount 1.0; schem:currency "USD".

Written using the following request:

curl 'https://vincent-test.solidcommunity.net/private/tmp/tripledoc-bug.ttl' -X PATCH -H 'Content-Type: application/sparql-update' --data-raw $' INSERT DATA {<https://vincent-test.solidcommunity.net/private/tmp/tripledoc-bug.ttl#160581889284507796464006133086> a <http://schema.org/MonetaryAmount>;\n    <http://schema.org/currency> "USD";\n    <http://schema.org/amount> "1"^^<http://www.w3.org/2001/XMLSchema#decimal>.\n};'

As far as I can tell I should be able to delete that data with the following PATCH:

DELETE DATA {<https://vincent-test.solidcommunity.net/private/tmp/tripledoc-bug.ttl#160581889284507796464006133086> a <http://schema.org/MonetaryAmount>;
    <http://schema.org/amount> "1.0"^^<http://www.w3.org/2001/XMLSchema#decimal>;
    <http://schema.org/currency> "USD".}; 

However, that results in the following response:

The patch could not be applied. Could not find to delete: https://vincent-test.solidcommunity.net/private/tmp/tripledoc-bug.ttl#160581889284507796464006133086 http://schema.org/amount "1.0"^^http://www.w3.org/2001/XMLSchema#decimal .

This appears to happen specifically with decimals. (Though it seems to be the problem has a similar root cause to https://github.com/solid/node-solid-server/issues/1468, but for decimals rather than booleans.)

See this sandbox for the reproduction (log in with a solidcommunity.net account): https://codesandbox.io/s/floral-glitter-jfejz?file=/src/index.ts

(Originally reported by @abigpotostew against Tripledoc.)