gform_pre_render errors when simply trying to get form ID

This should be simple... I'm trying to grab the form ID on the current page using gform_pre_render and then based on the form ID within the function gform_pre_render is calling do some work... (I don't always know which form is going to be loaded on the page) - so here's the simple version of the code:

$i_this_form_id = add_filter("gform_pre_render", "update_the_fields");
echo $i_this_form_id;

function update_the_fields ($form){
	return $form["id"];
}

The thing is - no matter what I do or don't do with the gform_pre_render - it just puts a whole bunch of " Invalid argument supplied for foreach()" errors on my form. BUT the echo in there returns the correct form ID.
Is there a better way to make the determination of which form loaded on a page by ID so I can then run the correct gform_field_value_* operation on the form? This seems to work but there's all those errors where the form goes - why?

This code (and a bunch more) lives in an include across a series of multiple pages. Based on the page that loads there's a different form. Since this is include code - I need to know WHICH form is on that page and then do certain things based on the form ID.
And here's the thing... line 2 above WORKS - the displayed value is the form ID.
The PRESENCE of the add_filter (setting a variable or not) causes the errors

add_filter("gform_pre_render", "update_the_fields");

results in many:
Warning: Invalid argument supplied for foreach() in /home/thisguy/public_html/wp-content/plugins/gravityforms/form_display.php on line X or Y or Z

Ultimately what I need to do is invoke a series of add_filter("gform_field_value_FIELDX", "populate_FIELDX"); for the unique fields on each unique form.