views: Prevent zero or negative size partitions

Defining a partition size <1 causes the partition to show with
a different configuration to the one configured in the form.
Any <1 size partition shows as Linux, Empty and the size field
without value.
Validate the form so we refuse any partition with size <1.

ogcp/views.py

@@ -653,6 +653,10 @@ def action_setup_modify():
                 flash(_('The EFI partition requires a FAT32 filesystem'), category='error')
                 return redirect(url_for('commands'))
 
+            if partition.size.data <= 0:
+                flash(_('Partitions can\'t have a size of zero or lower'), category='error')
+                return redirect(url_for('commands'))
+
         if cache_count == 0:
             flash(_(f'Missing cache partition'), category='error')
             return redirect(url_for('commands'))