Set tshortfall to 0 if it should exists but is not provided

app/services/imports/case_logs_import_service.rb

@@ -125,7 +125,7 @@ module Imports
       attributes["tcharge"] = safe_string_as_decimal(xml_doc, "Q18av")
 
       attributes["hbrentshortfall"] = unsafe_string_as_integer(xml_doc, "Q18d")
-      attributes["tshortfall"] = safe_string_as_decimal(xml_doc, "Q18dyes")
+      attributes["tshortfall"] = tshortfall(xml_doc, attributes)
 
       attributes["voiddate"] = compose_date(xml_doc, "VDAY", "VMONTH", "VYEAR")
       attributes["mrcdate"] = compose_date(xml_doc, "MRCDAY", "MRCMONTH", "MRCYEAR")
@@ -513,5 +513,12 @@ module Imports
     def people_with_details(xml_doc)
       ((2..8).map { |x| string_or_nil(xml_doc, "P#{x}Rel") } + [string_or_nil(xml_doc, "P1Sex")]).compact
     end
+
+    def tshortfall(xml_doc, attributes)
+      shortfall = safe_string_as_decimal(xml_doc, "Q18dyes")
+      return 0 if shortfall.blank? && attributes["hbrentshortfall"] == 1
+
+      shortfall
+    end
   end
 end

spec/fixtures/softwire_imports/case_logs/0ead17cb-1668-442d-898c-0d52879ff592.xml

@@ -166,7 +166,7 @@
     <Q18aiv override-field=""/>
     <Q18av override-field="">438.11</Q18av>
     <Q18d>1 Yes</Q18d>
-    <Q18dyes override-field="">7.00</Q18dyes>
+    <Q18dyes override-field="true"/>
     <Q19void>2021-09-30</Q19void>
     <Q19repair/>
     <Q20 override-field="">0</Q20>