Do not add docks if self.iface is not defined when using qgis_process

[Gustry]

To avoid the Python error with qgis_process :

➜ qgis_process run native:atlaslayouttomultiplepdf --distance_units=meters --area_units=m2 --ellipsoid=NONE --project_path=/home/etienne/dev/python/lizmap-plugin/lizmap/test/data/lizmap_3_3.qgs --LAYOUT=landscape --COVERAGE_LAYER=/home/etienne/dev/python/lizmap-plugin/lizmap/test/data/lines.geojson --FILTER_EXPRESSION= --SORTBY_EXPRESSION= --SORTBY_REVERSE=false --FORCE_VECTOR=false --FORCE_RASTER=false --GEOREFERENCE=true --INCLUDE_METADATA=true --DISABLE_TILED=false --SIMPLIFY=true --TEXT_FORMAT=0 --IMAGE_COMPRESSION=0 --OUTPUT_FILENAME= --OUTPUT_FOLDER=/tmp/
Traceback (most recent call last):
  File "/home/etienne/.local/share/QGIS/QGIS3/profiles/default/python/plugins/DataPlotly/gui/dock.py", line 131, in addDocksFromProject
    self.iface.mainWindow().restoreGeometry(self.geometry)
AttributeError: 'NoneType' object has no attribute 'mainWindow'

For sure, a lot of code execution can be avoided with qgis_process with these Dock.

[ghtmtt]

thanks for the addition @Gustry