Unquoted number for url name causes Logstash to crash

[n0othing]

Version: 7.8.0

Specifying an unquoted number as a URL name causes Logstash to crash. The following config:

input {
  http_poller {
  urls => { 1 => "http://svc.metrotransit.org/NexTrip/VehicleLocations/5?format=json" }
  request_timeout => 60
  schedule => { cron => "* * * * * UTC"}
  codec => "json"
  }
}

output {
  stdout { codec => rubydebug }
}

Causes Logstash to throw the following error:

logstash-7.8.0 bin/logstash -f logstash.conf
Sending Logstash logs to /Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logs which is now configured via log4j2.properties
[2020-06-23T11:29:34,379][WARN ][logstash.config.source.multilocal] Ignoring the 'pipelines.yml' file because modules or command line options are specified
[2020-06-23T11:29:34,495][INFO ][logstash.runner          ] Starting Logstash {"logstash.version"=>"7.8.0", "jruby.version"=>"jruby 9.2.11.1 (2.5.7) 2020-03-25 b1f55b1a40 Java HotSpot(TM) 64-Bit Server VM 25.181-b13 on 1.8.0_181-b13 +indy +jit [darwin-x86_64]"}
[2020-06-23T11:29:36,137][INFO ][org.reflections.Reflections] Reflections took 38 ms to scan 1 urls, producing 21 keys and 41 values 
[2020-06-23T11:29:36,321][ERROR][logstash.agent           ] Failed to execute action {:action=>LogStash::PipelineAction::Create/pipeline_id:main, :exception=>"Java::JavaLang::IllegalStateException", :message=>"Unable to configure plugins: (RuntimeError) can't add a new key into hash during iteration", :backtrace=>["org.logstash.config.ir.CompiledPipeline.<init>(CompiledPipeline.java:119)", "org.logstash.execution.JavaBasePipelineExt.initialize(JavaBasePipelineExt.java:80)", "org.logstash.execution.JavaBasePipelineExt$INVOKER$i$1$0$initialize.call(JavaBasePipelineExt$INVOKER$i$1$0$initialize.gen)", "org.jruby.internal.runtime.methods.JavaMethod$JavaMethodN.call(JavaMethod.java:837)", "org.jruby.ir.runtime.IRRuntimeHelpers.instanceSuper(IRRuntimeHelpers.java:1169)", "org.jruby.ir.runtime.IRRuntimeHelpers.instanceSuperSplatArgs(IRRuntimeHelpers.java:1156)", "org.jruby.ir.targets.InstanceSuperInvokeSite.invoke(InstanceSuperInvokeSite.java:39)", "Users.robbie.elastic.$7_dot_8_logstash_http_poller.logstash_minus_7_dot_8_dot_0.logstash_minus_core.lib.logstash.java_pipeline.RUBY$method$initialize$0(/Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logstash-core/lib/logstash/java_pipeline.rb:43)", "org.jruby.internal.runtime.methods.CompiledIRMethod.call(CompiledIRMethod.java:82)", "org.jruby.internal.runtime.methods.MixedModeIRMethod.call(MixedModeIRMethod.java:70)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:332)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:86)", "org.jruby.RubyClass.newInstance(RubyClass.java:939)", "org.jruby.RubyClass$INVOKER$i$newInstance.call(RubyClass$INVOKER$i$newInstance.gen)", "org.jruby.ir.targets.InvokeSite.invoke(InvokeSite.java:207)", "Users.robbie.elastic.$7_dot_8_logstash_http_poller.logstash_minus_7_dot_8_dot_0.logstash_minus_core.lib.logstash.pipeline_action.create.RUBY$method$execute$0(/Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logstash-core/lib/logstash/pipeline_action/create.rb:52)", "Users.robbie.elastic.$7_dot_8_logstash_http_poller.logstash_minus_7_dot_8_dot_0.logstash_minus_core.lib.logstash.pipeline_action.create.RUBY$method$execute$0$__VARARGS__(/Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logstash-core/lib/logstash/pipeline_action/create.rb)", "org.jruby.internal.runtime.methods.CompiledIRMethod.call(CompiledIRMethod.java:82)", "org.jruby.internal.runtime.methods.MixedModeIRMethod.call(MixedModeIRMethod.java:70)", "org.jruby.ir.targets.InvokeSite.invoke(InvokeSite.java:207)", "Users.robbie.elastic.$7_dot_8_logstash_http_poller.logstash_minus_7_dot_8_dot_0.logstash_minus_core.lib.logstash.agent.RUBY$block$converge_state$2(/Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logstash-core/lib/logstash/agent.rb:342)", "org.jruby.runtime.CompiledIRBlockBody.callDirect(CompiledIRBlockBody.java:138)", "org.jruby.runtime.IRBlockBody.call(IRBlockBody.java:58)", "org.jruby.runtime.IRBlockBody.call(IRBlockBody.java:52)", "org.jruby.runtime.Block.call(Block.java:139)", "org.jruby.RubyProc.call(RubyProc.java:318)", "org.jruby.internal.runtime.RubyRunnable.run(RubyRunnable.java:105)", "java.lang.Thread.run(Thread.java:748)"]}
warning: thread "Converge PipelineAction::Create<main>" terminated with exception (report_on_exception is true):
LogStash::Error: Don't know how to handle `Java::JavaLang::IllegalStateException` for `PipelineAction::Create<main>`
          create at org/logstash/execution/ConvergeResultExt.java:129
             add at org/logstash/execution/ConvergeResultExt.java:57
  converge_state at /Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logstash-core/lib/logstash/agent.rb:355
[2020-06-23T11:29:36,331][ERROR][logstash.agent           ] An exception happened when converging configuration {:exception=>LogStash::Error, :message=>"Don't know how to handle `Java::JavaLang::IllegalStateException` for `PipelineAction::Create<main>`", :backtrace=>["org/logstash/execution/ConvergeResultExt.java:129:in `create'", "org/logstash/execution/ConvergeResultExt.java:57:in `add'", "/Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logstash-core/lib/logstash/agent.rb:355:in `block in converge_state'"]}
[2020-06-23T11:29:36,367][FATAL][logstash.runner          ] An unexpected error occurred! {:error=>#<LogStash::Error: Don't know how to handle `Java::JavaLang::IllegalStateException` for `PipelineAction::Create<main>`>, :backtrace=>["org/logstash/execution/ConvergeResultExt.java:129:in `create'", "org/logstash/execution/ConvergeResultExt.java:57:in `add'", "/Users/robbie/elastic/7.8_logstash_http_poller/logstash-7.8.0/logstash-core/lib/logstash/agent.rb:355:in `block in converge_state'"]}
[2020-06-23T11:29:36,387][ERROR][org.logstash.Logstash    ] java.lang.IllegalStateException: Logstash stopped processing because of an error: (SystemExit) exit

This doesn't happen if the number is quoted (e.g "1"). Unquoted strings (e.g myurl) seem to work fine too.