PR# 19562 EiffelBuild Exception while editing SpinButton widget properties

Problem Report Summary
Submitter: rwschlatter
Category: EiffelBuild
Priority: High
Date: 2019/08/11
Class: Bug
Severity: Serious
Number: 19562
Release: 19.05 GPL
Confidential: No
Status: Closed
Environment: win 8.1 pro
Synopsis: EiffelBuild Exception while editing SpinButton widget properties

Attached minmal EiffelBuild project StepTwo

Has window containing two spin buttons and ok/cancel.
I open the Display window to see how it looks like.
Renamed the three widgets,
Then tinkered with spin buttons, first resized minimums, next  at whim chose to tinker with "y" spin button. 
In the properties I see the field "Text", so in my naivety I started to type an "x".

Eiffelbuild throws a tantrum and an exception trace at me.

The Display window shows the "x" where I believe a numeric / number is expected.
To Reproduce
As above.
Problem Report Interactions
From:jfiat_es    Date:2019/08/28    Status: Closed    Download   

From:rwschlatter    Date:2019/08/17    Status: Open    Download   

Attachment: build_project.bpr     Size:899
Attachment: Exception Trace 4 re Confirmation 2.txt     Size:8819
Attachment: StepThree dotnet estudio bug report trace.txt     Size:8392
Attachment: StepThree dotnet estudio call stack.png     Size:38378
Attachment: StepThree dotnet estudio object list.png     Size:51071
Attachment: StepThree dotnet estudio outputs.png     Size:22715
Attachment: StepThree dotnet exception trace.txt     Size:11035
Attachment: system_interface.xml     Size:30167
From:rwschlatter    Date:2019/08/16    Status: Open    Download   

From:rwschlatter    Date:2019/08/16    Status: Open    Download   

Attachment: Buider window exception with text field edit.txt     Size:4919
Attachment: build_project.bpr     Size:901
Attachment: Builder window exception with text field edit.png     Size:52900
Attachment: Program start exception Exception Trace.txt     Size:7649
Attachment: StepFour tracking the bug - marked.png     Size:60346
Attachment: system_interface.xml     Size:1392
From:rwschlatter    Date:2019/08/12    Status: Open    Download   

Attachment: After ignoring exception after text change.png     Size:101404
Attachment: After ignoring exception before text change.png     Size:125284
Attachment: Application after Eiffel compilation.png     Size:27067
Attachment:     Size:12147
Attachment: exception trace while modyfing text.txt     Size:51571
Attachment: TEXT_FIELD Monday (after).png     Size:83289
Attachment: TEXT_FIELD Monday (heading).png     Size:109191
Attachment: Uncaught Exception at start.png     Size:39308
Attachment: Uncaught Exception at start.txt     Size:8585
From:rwschlatter    Date:2019/08/11    Download   

Attachment: build_project.bpr     Size:783
Attachment: Display Window.png     Size:3891
Attachment: Exception Trace.txt     Size:8675
Attachment: Exception Window.png     Size:17215
Attachment: StepTwo project.png     Size:55545
Attachment: system_interface.xml     Size:5349