Selecting AltClosedGripperNose backgauge mode threw a NullReferenceException on Twinmatic-family configs (JornsTwinmaticClosedLoop, V2, V3, JornsHyperDriveFlexTwinmatic) when generating sequences/operations. JornsHyperDriveFlex was unaffected because its AltGripper axis is disabled, so the broken code path never ran.

Root cause: FoldingSolution.cs:341-342 dereferences parameters.AltGripperNoseGaugingOffset.CurrentValue and parameters.BackgaugeMinimumPositionWithAltGripperExtended.CurrentValue. Param 872 (AltGripperNoseGaugingOffset) was missing from every Twinmatic config, so the property returned null ? NPE.

Changes

Configs — added param 872 (Alt Gripper Nose Gauging Offset, default 0.25, modeled after param 871) to the 4 Twinmatic-named ConfigurationStore.json files. Resources — added AltGripperNoseGaugingOffset and AltGripperNoseGaugingOffsetDescription strings to ParameterResource.resx so the new param shows a friendly UI label. Code (defensive) — extended the null-guard pattern at FoldingSolution.cs:336 so the constraint is skipped (rather than crashing) if BackgaugeMinimumPositionWithAltGripperExtended or AltGripperNoseGaugingOffset is null in any future config.