validate cascade node feature index before init

[metsw24-max]

Out-of-bounds feature index in cascade nodes

DetectionLoadStringXml parses untrusted cascade XML and stores each weak-classifier nodes featureIdxstraight from theinternalNodestext, with no range check. That index is later used to look a feature up:CreateHidHaarreadsdata.haarFeatures[node.featureIdx]during init, and the LBP predictor indexeshid.features[node->featureIdx]. A cascade whose node points past the parsed feature list (or a negative value) therefore reads off the end of the vector. With ASan a node index of 999999against a single feature faults atSimdBaseDetection.cpp:393inCreateHidHaar`.

The recently merged rect checks guarded the per-rect value vectors but not this node-to-feature reference, so it was still reachable. Validating the index once in the loader keeps the rejection at the parse boundary and covers both the HAAR and LBP paths. I have kept it to a range check raising the existing SIMD_EX; valid cascades are unaffected.