Open help-window in modeldesigner fails

[EulenspiegelTill]

Describe the bug
When editing a model in the modeldesigner, your're editing a processing function and you need some additional advice. You try to click the Help Button. Then a error occurs.

How to Reproduce

1. Go to modeldesigner and edit a model
2. open a processing window in the designer
3. click the help button
4. See error -->

An error has occurred while executing Python code: 

AttributeError: 'ModelerParametersDialog' object has no attribute 'algorithm' 
Traceback (most recent call last):
  File "/Applications/QGIS.app/Contents/MacOS/../Resources/python/plugins/processing/modeler/ModelerParametersDialog.py", line 160, in openHelp
    self.widget.algorithm().provider().helpId(), self.algorithm().groupId(),
AttributeError: 'ModelerParametersDialog' object has no attribute 'algorithm'


Python version: 3.7.7 (default, Sep 22 2020, 10:25:18) [Clang 12.0.0 (clang-1200.0.32.2)] 
QGIS version: 3.16.1-Hannover Hannover, 3ecbe06f78 

Python Path:
/Applications/QGIS.app/Contents/MacOS/../Resources/python
/Users/tillweber/Library/Application Support/QGIS/QGIS3/profiles/Till_Oester/python
/Users/tillweber/Library/Application Support/QGIS/QGIS3/profiles/Till_Oester/python/plugins
/Applications/QGIS.app/Contents/MacOS/../Resources/python/plugins
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/pyproj-2.6.0-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/rasterio-1.1.5-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/snuggs-1.4.7-py3.7.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/opencv_contrib_python-4.3.0.36-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/cftime-1.2.1-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/affine-2.3.0-py3.7.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/patsy-0.5.1-py3.7.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/click_plugins-1.1.1-py3.7.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/numba-0.50.1-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/pandas-1.1.0-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/lib-dynload
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/Rtree-0.9.4-py3.7.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/geopandas-0.8.1-py3.7.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/matplotlib-3.3.0-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/scipy-1.5.1-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/numpy-1.19.1-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/Fiona-1.8.13.post1-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/Pillow-7.2.0-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/netCDF4-1.5.3-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python37.zip
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/GDAL-3.1.2-py3.7-macosx-10.13.0-x86_64.egg
/Applications/QGIS.app/Contents/MacOS/lib/python3.7/site-packages/statsmodels-0.11.1-py3.7-macosx-10.13.0-x86_64.egg
/Users/tillweber/Library/Application Support/QGIS/QGIS3/profiles/Till_Oester/python
/Users/tillweber/Desktop/201127_Phyton_Kurs/data/profile

QGIS and OS versions

QGIS version	3.16.1-Hannover	QGIS code revision	3ecbe06
Compiled against Qt	5.14.2	Running against Qt	5.14.2
Compiled against GDAL/OGR	3.1.2	Running against GDAL/OGR	3.1.2
Compiled against GEOS	3.8.1-CAPI-1.13.3	Running against GEOS	3.8.1-CAPI-1.13.3
Compiled against SQLite	3.31.1	Running against SQLite	3.31.1
PostgreSQL Client Version	12.3	SpatiaLite Version	4.3.0a
QWT Version	6.1.4	QScintilla2 Version	2.11.4
Compiled against PROJ	6.3.2	Running against PROJ	Rel. 6.3.2, May 1st, 2020
OS Version	macOS High Sierra (10.13)
Active python plugins	ORStools; quick_map_services; swiss_locator; db_manager; processing; qfieldsync; profile_plugin

Additional context

[EulenspiegelTill]

@m-kuhn error which occurred in lecture

[gioman]

Confirmed also on Windows 10, does not happens on 3.10.

[roya0045]

This is a quick fix, I'll do a PR in a few moments.

[roya0045]

@EulenspiegelTill Thanks for reporting.