As this error occurs only with integer the workaround consists in cast the type to string before use in the chart.

1. Create dataset (using MySQL syntax here, but similar syntax should be available for other DBs):
select id, processInstanceId, processInstanceDescription, convert(slaCompliance, char(50)) as slaComplianceString from ProcessInstanceLog

2. Create a new page with a pie chart, use column 'slaComplianceString' for Categories

1 - Create a dataset

• Administration -> Data Sets
• New Data Set -> Execution Server
• Data:
  Name: getAllProcesses
  DS: ${org.kie.server.persistence.ds}
  Server configuration: default-kieserver (or any other running kie-server)
  Query Target: PROCESS
  Query: select * from ProcessInstanceLog
• Test & Save the new dataset

2. Create a page

• Menu -> Pages -> New Page
• Expand 'Reporting'
• Drag a Pie chart on to the page
• Select the 'Data' tab, set:
  Dataset: getAllProcesses
  Categories: slaCompliance ==> THIS IS THE IMPORTANT STEP, the error only shows up when selecting specific columns for the category
  Series: processInstanceId
  Aggregate function: Count