[mlir][sparse] fix compiler warning when using release build.

mlir/lib/Dialect/SparseTensor/Transforms/Sparsification.cpp

static bool isInvariantAffine(const CodeGen &codegen, AffineExpr a,
                               unsigned ldx, bool &atLevel) {
   return isInvariantAffine(a, codegen.getLoopCurStack(), ldx, atLevel);
 }
 
 /// Helper method to construct a permuted dimension ordering
 /// that adheres to the given topological sort.
 static AffineMap permute(const Merger &merger, MLIRContext *context,
                          AffineMap m, ArrayRef<unsigned> topSort) {
-  unsigned sz = topSort.size();
-  assert(m.getNumDims() + merger.getNumFilterLoops() == sz &&
+  assert(m.getNumDims() + merger.getNumFilterLoops() == topSort.size() &&
          "TopoSort/AffineMap size mismatch");
   // Construct the inverse of `m`; to avoid the asymptotic complexity
   // of calling `m.getPermutedPosition` repeatedly.
   SmallVector<unsigned> perm;
   unsigned numResults = m.getNumResults();
   BitVector worklist(numResults, true);
   unsigned loopDepth = 1;