Fixes a panic when reading an instance fleet with an empty `launch_specifications` argument.
```console
% make testacc PKG=emr TESTS=TestAccEMRCluster_
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go1.22.6 test ./internal/service/emr/... -v -count 1 -parallel 20 -run='TestAccEMRCluster_' -timeout 360m
--- PASS: TestAccEMRCluster_basic (434.89s)
=== CONT TestAccEMRCluster_autoTerminationPolicy
--- PASS: TestAccEMRCluster_Step_basic (458.24s)
=== CONT TestAccEMRCluster_MasterInstanceGroup_instanceCount
--- PASS: TestAccEMRCluster_sJSON (463.57s)
=== CONT TestAccEMRCluster_security
--- PASS: TestAccEMRCluster_additionalInfo (478.89s)
=== CONT TestAccEMRCluster_MasterInstanceGroup_name
--- PASS: TestAccEMRCluster_disappears (497.97s)
=== CONT TestAccEMRCluster_MasterInstanceGroup_instanceType
--- PASS: TestAccEMRCluster_CoreInstanceGroup_autoScalingPolicy (588.15s)
=== CONT TestAccEMRCluster_Kerberos_clusterDedicatedKdc
--- PASS: TestAccEMRCluster_InstanceFleetMaster_only (670.75s)
=== CONT TestAccEMRCluster_MasterInstanceGroup_bidPrice --- PASS: TestAccEMRCluster_StepConcurrency_level (724.43s)
=== CONT TestAccEMRCluster_terminationProtected
--- PASS: TestAccEMRCluster_s3LogEncryption (759.72s)
=== CONT TestAccEMRCluster_s3Logging
--- PASS: TestAccEMRCluster_unhealthyNodeReplacement (792.17s)
=== CONT TestAccEMRCluster_Bootstrap_ordering
--- PASS: TestAccEMRCluster_tags (793.52s)
=== CONT TestAccEMRCluster_visibleToAllUsers
--- PASS: TestAccEMRCluster_Step_mode (837.79s)
=== CONT TestAccEMRCluster_PlacementGroupConfigs
--- PASS: TestAccEMRCluster_CoreInstanceGroup_instanceType (864.33s) === CONT TestAccEMRCluster_keepJob
--- PASS: TestAccEMRCluster_RootVolume_size (896.28s)
=== CONT TestAccEMRCluster_EC2Attributes_defaultManagedSecurityGroups
--- PASS: TestAccEMRCluster_security (464.92s)
=== CONT TestAccEMRCluster_Step_multiple_listStates
--- PASS: TestAccEMRCluster_CoreInstanceGroup_bidPrice (1007.29s)
=== CONT TestAccEMRCluster_Step_multiple
--- PASS: TestAccEMRCluster_terminationProtected (389.17s)
--- PASS: TestAccEMRCluster_MasterInstanceGroup_instanceType (678.07s)
--- PASS: TestAccEMRCluster_Kerberos_clusterDedicatedKdc (614.73s)
--- PASS: TestAccEMRCluster_MasterInstanceGroup_name (737.79s)
--- PASS: TestAccEMRCluster_CoreInstanceGroup_name (1229.11s)
--- PASS: TestAccEMRCluster_keepJob (401.33s)
--- PASS: TestAccEMRCluster_Step_multiple_listStates (417.17s)
--- PASS: TestAccEMRCluster_autoTerminationPolicy (925.32s)
=== NAME TestAccEMRCluster_visibleToAllUsers
cluster_test.go:1296: Step 3/4 error: Check failed: Check 2/2 error: aws_emr_cluster.test: Attribute 'visible_to_all_users' expected "false", got "true"
--- PASS: TestAccEMRCluster_s3Logging (633.74s)
--- PASS: TestAccEMRCluster_Step_multiple (395.48s)
--- PASS: TestAccEMRCluster_MasterInstanceGroup_instanceCount (961.03s)
--- PASS: TestAccEMRCluster_PlacementGroupConfigs (628.98s)
--- FAIL: TestAccEMRCluster_visibleToAllUsers (712.97s)
--- PASS: TestAccEMRCluster_MasterInstanceGroup_bidPrice (847.10s)
--- PASS: TestAccEMRCluster_CoreInstanceGroup_instanceCount (1612.28s)
--- PASS: TestAccEMRCluster_Bootstrap_ordering (1107.51s)
--- PASS: TestAccEMRCluster_InstanceFleet_basic (2024.62s)
--- PASS: TestAccEMRCluster_EC2Attributes_defaultManagedSecurityGroups (1842.94s)
=== NAME TestAccEMRCluster_ebs
cluster_test.go:1539: Step 1/2 error: Error running apply: exit status 1
Error: waiting for EMR Cluster (j-33UEO2SNMV9LX) to create: unexpected state 'TERMINATING', wanted target 'RUNNING, WAITING'. last error: INTERNAL_ERROR: Failed to start the job flow due to an internal error
with aws_emr_cluster.test,
on terraform_plugin_test.tf line 194, in resource "aws_emr_cluster" "test":
194: resource "aws_emr_cluster" "test" {
--- FAIL: TestAccEMRCluster_ebs (2950.94s)
=== NAME TestAccEMRCluster_CustomAMI_id
cluster_test.go:1573: Step 1/2 error: Error running apply: exit status 1
Error: waiting for EMR Cluster (j-4KYO8528ZP33) to create: unexpected state 'TERMINATING', wanted target 'RUNNING, WAITING'. last error: INTERNAL_ERROR: Failed to start the job flow due to an internal error
with aws_emr_cluster.test,
on terraform_plugin_test.tf line 305, in resource "aws_emr_cluster" "test":
305: resource "aws_emr_cluster" "test" {
--- FAIL: TestAccEMRCluster_CustomAMI_id (2995.13s)
FAIL
FAIL github.com/hashicorp/terraform-provider-aws/internal/service/emr 3001.300s
```
Test failures are pre-existing and not related to this change.