Fix #1974: assertion when reserving an empty sparse matrix
diff --git a/test/sparse_basic.cpp b/test/sparse_basic.cpp
index 9e735b3..5f87621 100644
--- a/test/sparse_basic.cpp
+++ b/test/sparse_basic.cpp
@@ -662,6 +662,14 @@
     iters[0] = IteratorType(m2,0);
     iters[1] = IteratorType(m2,m2.outerSize()-1);
   }
+
+  // test reserve with empty rows/columns
+  {
+    SparseMatrixType m1(0,cols);
+    m1.reserve(ArrayXi::Constant(m1.outerSize(),1));
+    SparseMatrixType m2(rows,0);
+    m2.reserve(ArrayXi::Constant(m2.outerSize(),1));
+  }
 }