Fix the vertical alignment of overunder symbols.

When an overunder symbol has a subscript, it goes below the symbol, and the baseline of the Vlist thus created is actually the baseline of the lowest item in the Vlist. Hence, it must be moved only if there is a subscript, and not otherwise.

Author: tfpf

lib/matplotlib/_mathtext.py

@@ -2200,9 +2200,9 @@ def subsuper(self, s, loc, toks):
                 hlist = HCentered([sub])
                 hlist.hpack(width, 'exactly')
                 vlist.extend([Vbox(0, vgap), hlist])
-                shift = hlist.height + vgap
+                shift = hlist.height + vgap + nucleus.depth
             vlist = Vlist(vlist)
-            vlist.shift_amount = shift + nucleus.depth
+            vlist.shift_amount = shift
             result = Hlist([vlist])
             return [result]