Some SimpleCRM menu items fail with error: Call to a member function getModel() on null

Question

Immediately after upgrading my Joomla version from 3.9.1 to 3.9.4, I can no longer access certain Simple CRM submenus in the backend.

The Company Codes link works properly.
(http://localhost/jdem02/administrator/index.php?option=com_gscrm&view=Codes)

The following do not:

• Simple CRM
  (http://localhost/jdem02/administrator/index.php?option=com_gscm)

• User Management
  (http://localhost/jdem02/administrator/index.php?option=com_gscrm&view=Beads)

• User Roles
  (http://localhost/jdem02/administrator/index.php?option=com_gscrm&view=Roles)

• Currencies & Rates
  (http://localhost/jdem02/administrator/index.php?option=com_gscrm&view=Currencies)

They all generate the same error:

0 Call to a member function getModel() on null
C:\wamp64\www\jdem02\libraries\fof30\Form\Field\Numeric.php:25

So who moved my cheese?

How do I fix this?

p.s. I am not interested in lowering my Joomla version.

---

Update:

This is my administrator/components/com_gscrm/View directory structure:

Here is the Roles form.default.xml script:

<?xml version="1.0" encoding="UTF-8"?>
<form type="browse" 
    show_header="1" 
        show_filters="1" 
            show_pagination="1" 
                norows_placeholder="COM_GSCRM_COMMON_NORECORDS">
  <headerset>
    <header name="gscrm_role_id" type="RowSelect" label="COM_GSCRM_ROLES_GSCRM_ROLE_ID_LABEL" />
    <header name="role_id" label="COM_GSCRM_ROLES_GSCRM_ROLE_ID_LABEL" description="COM_GSCRM_ROLES_GSCRM_ROLE_ID_DESC"/>         
    <header name="title" type="Searchable" label="COM_GSCRM_ROLES_TITLE_LABEL"/>
    <header name="parent" label="COM_GSCRM_ROLES_PARENT_LABEL" sortable="true"/>
    <header name="child" label="COM_GSCRM_ROLES_CHILD_LABEL" sortable="true"/>
    <header name="code" type="Searchable" label="COM_GSCRM_ROLES_CODE_LABEL" sortable="true"/>
    <header name="enabled" type="Published" label="COM_GSCRM_ROLES_ENABLED_LABEL" sortable="true"/>
    <header name="access" type="AccessLevel" label="COM_GSCRM_ROLES_ACCESS_LABEL" sortable="true"/>
  </headerset>

  <fieldset name="items">
    <field name="gscrm_role_id" type="SelectRow"/>
    <field name="gscrm_role_id" id="role_id" type="text"/>

    <field name="title" type="Sortable" url="index.php?option=com_gscrm&amp;view=Role&amp;id=[ITEM:ID]&amp;[TOKEN]=1"/>

    <field name="parent" type="Numeric"/>
    <field name="child" type="Numeric"/>

    <field name="code" type="ViewTemplate" emptylabel="1" 
                        source="admin:com_gscrm/Beads/Code_name" 
    />  
    <field name="enabled" type="Actions"/>
    <field name="access" type="AccessLevel"/>
  </fieldset>
</form>

Answer 1

This question (problem) was successfully and quite quickly solved yesterday, working effectively together with @Mick on the solution. And this question is very well detailed, well described and it included the exact error message from Joomla, so it is a good example of a well-built question on SE.

The solution was relatively simple: we had to change the deprecated numeric type form field to number type form field in the XML files where these fields are defined in Joomla and in FOF too.

At form field definitions using type=”number” instead of type=”numeric” solved the problem quite straightforwardly.

Short description about the problem and solution:

The error message displayed two important things: 1. which file the error occurred in (at which line exactly) 2. And it also made obvious that the component is built with using FOF (Framework on Framework), with classes found in fof30 library in Joomla 3 .

When we open the particular file noticed in the error message, we find that file would be about constructing a form field and we can also see immediately that the field is deprecated with a message:

Backwards compatibility field. DO NOT USE IN PHP 7.2 AND LATER.

And with an added note: @deprecated 3.1

If you then check the fof30 library, you will find that the fof version number now is: 3.4.2.

Finally, we can also find a very helpful message in the file, thanks to the creator of FOF: “…Use the number field type instead.”

Thus in this numeric field class, the field fails to be constructed, but if you change the form field type to number in the corresponding XML files where the form and fields are built, then the problem should be solved. And it was so actually. One of the problematic XML file regarding the above explanation was also included by @Mick as an update of the question.