don't overwrite values in by heapifed tree

Author: rushabh-v

src/heaps/mutable_binary_heap.jl

@@ -136,10 +136,10 @@ function _make_mutable_binary_heap(ord::Ordering, ty::Type{T}, values) where T
     n = length(values)
     nodes = Vector{MutableBinaryHeapNode{T}}(undef, n)
     nodemap = Vector{Int}(undef, n)
-    values = heapify!(values, ord)
+    valtree = heapify!(values, ord)
 
     i::Int = 0
-    for v in values
+    for v in valtree
         i += 1
         @inbounds nodes[i] = MutableBinaryHeapNode{T}(v, i)
         @inbounds nodemap[i] = i