Yes it is safe to eat maple tree leaves.
The maple tree is mostly know for it's maple syrup which is edible.
But other parts of the maple tree are also edible and can be eaten.
You can eat the maple tree syrup, maple tree leaves, and even the maple tree seeds.
Maple Tree bark is also edible.
Even other leaves on some other trees are edible and even the tree bark on most other trees can be eaten as well.
I have a wilderness survival book that says that you can eat the tree bark and leaves of most any tree that is out in the wilderness.