[fixes] raise exception while deleting fiscal year if fiscal year is set as default in Global Settings and while calculating get_month_details if year_start_date not found

erpnext/accounts/doctype/fiscal_year/fiscal_year.py

@@ -40,6 +40,11 @@ class FiscalYear(Document):
 
 	def on_update(self):
 		check_duplicate_fiscal_year(self)
+	
+	def on_trash(self):
+		global_defaults = frappe.get_doc("Global Defaults")
+		if global_defaults.current_fiscal_year == self.name:
+			frappe.throw(_("You cannot delete Fiscal Year {0}. Fiscal Year {0} is set as default in Global Settings").format(self.name))
 
 @frappe.whitelist()
 def check_duplicate_fiscal_year(doc):

erpnext/hr/doctype/process_payroll/process_payroll.py

@@ -206,3 +206,5 @@ def get_month_details(year, month):
 			'month_end_date': med,
 			'month_days': month_days
 		})
+	else:
+		frappe.throw(_("Fiscal Year {0} not found").format(year))