opentelemetry.tracer crashes with TypeError in transaction with high number of spans #2245

from elasticapm.contrib.opentelemetry import trace
from elasticapm import Client, capture_span

import os

# Reduce number of spans required to reproduce the issue
ELASTIC_APM_TRANSACTION_MAX_SPANS = 10
STEPS_ABOVE = ELASTIC_APM_TRANSACTION_MAX_SPANS + 1 
STEPS_BELLOW = ELASTIC_APM_TRANSACTION_MAX_SPANS - 1 
os.environ["ELASTIC_APM_TRANSACTION_MAX_SPANS"] = str(ELASTIC_APM_TRANSACTION_MAX_SPANS)

apm_client = Client()
tracer = trace.get_tracer(__name__)

# Simulate deep nested spans
def capture_span_elasticapm(steps=10):
     if steps == 0:
        return
     
     with capture_span():
        capture_span_elasticapm(steps-1)

def capture_span_opentelemetry(steps=10):
     if steps == 0:
        return
     
     with tracer.start_as_current_span("test"):
        capture_span_opentelemetry(steps-1)


# TEST

# Works - Expected
transaction = apm_client.begin_transaction('processors')
capture_span_elasticapm(STEPS_BELLOW)
apm_client.end_transaction('myapp.billing_process')

# Works - Expected
transaction = apm_client.begin_transaction('processors')
capture_span_opentelemetry(STEPS_BELLOW)
apm_client.end_transaction('myapp.billing_process')

# Works - Expected
transaction = apm_client.begin_transaction('processors')
capture_span_elasticapm(STEPS_ABOVE)
apm_client.end_transaction('myapp.billing_process')

# Crashes - Unexpected 
# TypeError: 'NoneType' object does not support item assignment
transaction = apm_client.begin_transaction('processors')
capture_span_opentelemetry(STEPS_ABOVE)
apm_client.end_transaction('myapp.billing_process')