fix(FastSense): use Value field for scalar resolved thresholds

ResolvedThresholds with empty X/Y arrays are scalar thresholds
stored in the Value field. The previous fix tried th.Y(1) which
crashes on empty arrays. Now correctly uses th.Value for scalar
thresholds and falls back to th.Y(1) only if Value is empty.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: HanSur94

libs/FastSense/FastSense.m

@@ -575,22 +575,21 @@ function addSensor(obj, sensor, varargin)
                         thLabel = sprintf('Threshold %d', i);
                     end
                     [thColor, thStyle] = obj.resolveThresholdStyle(th.Color, th.LineStyle);
-                    if numel(th.X) <= 1
-                        % Single-point or scalar — use scalar form
-                        thVal = th.Y(1);
-                        obj.addThreshold(thVal, ...
-                            'Direction', th.Direction, ...
-                            'ShowViolations', true, ...
-                            'Label', thLabel, ...
-                            'Color', thColor, ...
-                            'LineStyle', thStyle);
+                    nvArgs = {'Direction', th.Direction, ...
+                        'ShowViolations', true, ...
+                        'Label', thLabel, ...
+                        'Color', thColor, ...
+                        'LineStyle', thStyle};
+                    if ~isempty(th.X) && numel(th.X) > 1
+                        % Time-varying threshold
+                        obj.addThreshold(th.X, th.Y, nvArgs{:});
                     else
-                        obj.addThreshold(th.X, th.Y, ...
-                            'Direction', th.Direction, ...
-                            'ShowViolations', true, ...
-                            'Label', thLabel, ...
-                            'Color', thColor, ...
-                            'LineStyle', thStyle);
+                        % Scalar threshold — use Value field
+                        thVal = th.Value;
+                        if isempty(thVal) && ~isempty(th.Y)
+                            thVal = th.Y(1);
+                        end
+                        obj.addThreshold(thVal, nvArgs{:});
                     end
                 end
             end