fix: Use get for conditionally available fields while setting missing values

[marination]

To Replicate Issue:

• Add custom field supplier in Material Request
• Create a new MR > Save > watch the world burn

Issue:

• Due to custom field "supplier" and missing field "supplier_address", dot operator breaks in buying_controller > set_missing_values > get_party_details

   File "apps/erpnext/erpnext/controllers/buying_controller.py", line 74, in set_missing_values
     doctype=self.doctype, company=self.company, party_address=self.supplier_address, 
     shipping_address=self.get('shipping_address'),
   AttributeError: 'MaterialRequest' object has no attribute 'supplier_address'

• This scenario is brought to you by customisation

Fix:

• Make sure to use get instead of just dot operator if field is in some doctypes and not all

Ambiguity:

• Adding such custom fields with core field names, triggers JS functions also that technically aren't supposed to be triggered. The user won't have a clue. Not sure how to go about that

[marination]

Skipping tests here, its a defensive fix

[codecov]

Codecov Report

Merging #29426 (78b6b29) into develop (108d104) will decrease coverage by 0.07%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop   #29426      +/-   ##
===========================================
- Coverage    57.99%   57.91%   -0.08%     
===========================================
  Files         1091     1091              
  Lines        67868    67868              
===========================================
- Hits         39357    39303      -54     
- Misses       28511    28565      +54     

Impacted Files	Coverage Δ
erpnext/controllers/buying_controller.py	87.02% <100.00%> (ø)
erpnext/utilities/product.py	14.70% <0.00%> (-35.30%)	⬇️
erpnext/shopping_cart/product_info.py	30.30% <0.00%> (-21.22%)	⬇️
.../manufacturing/report/bom_explorer/bom_explorer.py	94.44% <0.00%> (-5.56%)	⬇️
...ctype/woocommerce_settings/woocommerce_settings.py	80.76% <0.00%> (-3.85%)	⬇️
...eorder_level/itemwise_recommended_reorder_level.py	90.56% <0.00%> (-3.78%)	⬇️
erpnext/stock/report/stock_ledger/stock_ledger.py	74.79% <0.00%> (-3.26%)	⬇️
...e/shopping_cart_settings/shopping_cart_settings.py	66.03% <0.00%> (-1.89%)	⬇️
erpnext/stock/report/stock_ageing/stock_ageing.py	91.32% <0.00%> (-1.74%)	⬇️
erpnext/stock/reorder_item.py	76.06% <0.00%> (-1.71%)	⬇️
... and 20 more

[marination]

Gave it some thought. One way to go about controlling what is triggered where is to have a clear map of fields and documents.
But that is ultra tedious. We use where field is present in a lot of places.
Not worth the effort, ending it at this fix

[marination]

@Mergifyio backport version-13-hotfix

[mergify]

backport version-13-hotfix

✅ Backports have been created

• #29446 fix: Use get for conditionally available fields while setting missing values (backport #29426) has been created for branch version-13-hotfix