fix: AppBio QuantStudio Design & Analysis - Check for valid rq values before setting r_sample and r_target (#1138)

Co-authored-by: Nathan Stender <nathan.stender@benchling.com>

Author: slopez-b

src/allotropy/parsers/appbio_quantstudio_designandanalysis/appbio_quantstudio_designandanalysis_calculated_documents.py

@@ -391,7 +391,7 @@ def iter_standard_curve_calc_docs(
 
 def iter_relative_standard_curve_calc_docs(
     well_items: list[WellItem],
-    r_sample: str,
+    r_sample: str | None,
     r_target: str | None,
 ) -> Iterator[CalculatedDocument]:
     # Y-Intercept, Slope, Quantity, Amp score, Cq confidence,

src/allotropy/parsers/appbio_quantstudio_designandanalysis/structure/relative_standard_curve/creator.py

@@ -22,6 +22,20 @@
 )
 
 
+def _has_valid_rq_values(reader: DesignQuantstudioReader) -> bool:
+    """Return True if the RQ Replicate Group Result sheet contains at least one
+    non-null Rq value.
+
+    When all Rq values are null or nan (e.g. the reference calibrator sample
+    was not processed or all wells undetermined), the reference sample cannot be
+    inferred and RQ-derived calculated data documents must be skipped.
+    """
+    sheet = reader.get_non_empty_sheet_or_none("RQ Replicate Group Result")
+    if sheet is None or "Rq" not in sheet.columns:
+        return False
+    return bool(sheet["Rq"].notna().any())
+
+
 class RelativeStandardCurveCreator(Creator):
     PLUGIN_REGEX: ClassVar[str] = r"Relative Quantification"
     EXPECTED_SHEETS: ClassVar[list[str]] = [
@@ -34,8 +48,12 @@ def create(cls, reader: DesignQuantstudioReader) -> Data:
         wells = RelativeStandardCurveWellList.create(reader, header)
         well_items = wells.get_well_items()
 
-        r_sample = Result.get_reference_sample(reader)
-        r_target = Result.get_reference_target(reader)
+        if not _has_valid_rq_values(reader):
+            r_sample = None
+            r_target = None
+        else:
+            r_sample = Result.get_reference_sample(reader)
+            r_target = Result.get_reference_target(reader)
 
         return Data(
             header,