If URL has fragment, but no such URL with specified fragment
is present in contents tree, try to fallback to URL without any fragment
if such URL is present.

First test case, checking new behaviour:

1. In contents tree open: "Fundamentals" -> "Finding Your Way Around" -> "Common Menus"
2. Scroll down to "The Tools Menu" section and click "Check Spelling" link.
3. In contents tree "Common Tasks" item should be expanded and "Check Spelling" item should be selected.

Second test case, verifying that old behaviour is not broken:

1. In contents tree open: "Application Manuals" -> "System" -> "Dolphin"
2. In the table of contents on right side of application scroll down and click "3. Configuring Dolphin"
3. In contents tree "Dolphin" item should be expanded and "Configuring Dolphin" should be selected.
4. Click 'back' button, and in the table of contents on right side of application scroll down and click "The Dolphin Preferences Dialog"
5. In contents tree "Dolphin" and "Configuring Dolphin" items should be expanded and "The Dolphin Preferences Dialog" should be selected.