query-node: hotfix membership metadata handler

[mnaamani]

Processor failed handling invalid external resource type in membership update event:

INFO: Processing block: 0003698662-81aca, events count: 7 
ERROR: Stopping the proccessor due to errors: {} name: Error, message: Invalid ResourceType: false, stack: Error: Invalid ResourceType: false
    at asMembershipExternalResource (/joystream/query-node/mappings/lib/src/membership.js:38:15)
    at Array.flatMap (<anonymous>)
    at members_MemberProfileUpdated (/joystream/query-node/mappings/lib/src/membership.js:155:224)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
    at async MappingsLookupService.call (/joystream/node_modules/@joystream/hydra-processor/lib/executor/MappingsLookupService.js:80:9)
    at async /joystream/node_modules/@joystream/hydra-processor/lib/executor/TransactionalExecutor.js:41:17
INFO: Shutting down...
ERROR: {} name: Error, message: Error: Invalid ResourceType: false, stack: Error: Error: Invalid ResourceType: false
    at MappingsProcessor.processingLoop (/joystream/node_modules/@joystream/hydra-processor/lib/process/MappingsProcessor.js:75:23)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
    at async Promise.all (index 1)
    at async MappingsProcessor.start (/joystream/node_modules/@joystream/hydra-processor/lib/process/MappingsProcessor.js:25:9)
    at async ProcessorRunner.process (/joystream/node_modules/@joystream/hydra-processor/lib/start/ProcessorRunner.js:47:9)
    at async Run.run (/joystream/node_modules/@joystream/hydra-processor/lib/commands/run.js:27:13)
    at async Run._run (/joystream/node_modules/@oclif/command/lib/command.js:43:20)
    at async Config.runCommand (/joystream/node_modules/@oclif/config/lib/config.js:173:24)
    at async Main.run (/joystream/node_modules/@oclif/command/lib/main.js:27:9)
    at async Main._run (/joystream/node_modules/@oclif/command/lib/command.js:43:20)
INFO: Closing the database connection...
error Command failed with exit code 1.

Processing block https://polkadot.js.org/apps/#/explorer/query/0003698662

Patched version ignores invalid types.