Workaround chromium causing selection start to also change when end is changed in some circumstances

Fixes #2054934 [Extra text copied when selecting across pages](https://bugs.launchpad.net/calibre/+bug/2054934)

Author: kovidgoyal

src/pyj/select.pyj

@@ -228,13 +228,15 @@ def move_end_of_selection(pos, start):
         else:
             # point is inside the selection
             start = False
+    new_range = document.createRange()
     if start:
-        if r.startContainer is not p.offsetNode or r.startOffset is not p.offset:
-            r.setStart(p.offsetNode, p.offset)
-            sel.removeAllRanges()
-            sel.addRange(r)
+        new_range.setStart(p.offsetNode, p.offset)
+        new_range.setEnd(r.endContainer, r.endOffset)
+        other_boundary_changed = r.endContainer is not new_range.endContainer or r.endOffset is not new_range.endOffset
     else:
-        if r.endContainer is not p.offsetNode or r.endOffset is not p.offset:
-            r.setEnd(p.offsetNode, p.offset)
-            sel.removeAllRanges()
-            sel.addRange(r)
+        new_range.setStart(r.startContainer, r.startOffset)
+        new_range.setEnd(p.offsetNode, p.offset)
+        other_boundary_changed = r.startContainer is not new_range.startContainer or r.startOffset is not new_range.startOffset
+    if not new_range.collapsed or not other_boundary_changed:
+        sel.removeAllRanges()
+        sel.addRange(new_range)