Issue #16922: fixed findtext() to return empty Unicode string instead of empty bytes object when there's no text.

Patch by Serhiy Storchaka.
diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index c36af5d..17d5d09 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -840,7 +840,7 @@
 
             PyObject* text = element_get_text(item);
             if (text == Py_None)
-                return PyBytes_FromString("");
+                return PyUnicode_FromString("");
             Py_XINCREF(text);
             return text;
         }