The - i.e. dash symbol is not recognised in the JQL query when using issueFunction in dateCompare

Steps to Reproduce

1. Add two date fields to a project one for Delivery Date and another for Expected Date
2. Name either one or both of the date fields with a - i.e. dash symbol. For example Expected-Date
3. Create a few tickets with sample data and set the date values for these fields
4. Run a JQL query to filter the issue using the issueFunction in dateCompare filter

   issueFunction in dateCompare("","Expected-Date > Delivery Date")
   

Current Behaviour

1. When the JQL Query is executed an error message is returned i.e.,

   Scripted function "dateCompare" compilation failure. Contact administrator and check logs. Message: Field name: Expected not found or not a date or datetime.
   

   as shown in the image below:-
   
   and an error message is displayed in the log

   2020-08-06 17:49:33,998+0800 http-nio-9091-exec-14 ERROR admin 1069x1060x2 1pa1plw 0:0:0:0:0:0:0:1 /rest/issueNav/1/issueTable [c.o.j.groovy.jql.ScriptedJqlFunction] Script error for function: dateCompare.
   java.lang.Exception: Field name: Expected not found or not a date or datetime.
   	at com.onresolve.jira.groovy.jql.DateCompare.resolveField(DateCompare.groovy:215)
   	at com.onresolve.jira.groovy.jql.DateCompare.dateWindowParser(DateCompare.groovy:167)
   	at com.onresolve.jira.groovy.jql.DateCompare$dateWindowParser$0.callCurrent(Unknown Source)
   	at com.onresolve.jira.groovy.jql.DateCompare.dateCompareParser(DateCompare.groovy:231)
   	at com.onresolve.jira.groovy.jql.DateCompare$dateCompareParser.callCurrent(Unknown Source)
   	at com.onresolve.jira.groovy.jql.DateCompare.extractParameters(DateCompare.groovy:237)
   	at com.onresolve.jira.groovy.jql.DateCompare.validate(DateCompare.groovy:41)
   	at com.onresolve.jira.groovy.jql.JqlFunction$validate$6.call(Unknown Source)
   	at com.onresolve.jira.groovy.jql.ScriptedJqlFunction.validate(ScriptedJqlFunction.groovy:117)
   

Expected Behaviour

1. Even though a - i.e. dash character is included in the name of the field, it is expected to execute without any issue.
2. If the field with a dash is added into a basic JQL, it is able to execute without any problem for example:-