When there are multiple siteaccesses with different PathPrefix configurations, language switcher does not work properly:

• switching from a SA. using a path prefix to other one without
• switching from a SA. without a path prefix to other one with a path prefix
• Switching between siteaccesses using different path prefixes.

Steps to reproduce:

1. Setup 3 different siteaccesses: eng, fre, por
2. Setup content (use main language availability):
   1. Create a "TestFolder" folder under root (home)
   2. Create a "TestArticle" under "TestFolder"
   3. Translate "TestFolder" to "TestFolderFre" (fre-FR language)
3. Configure the PathPrefix setting in site.ini:
   1. in "eng" sa: TestFolder
   2. in "fre" sa: TestFolderFre
   3. in "por" sa: none (commented or empty setting)
4. clear (template) caches

Verify behavior:

• Access the site using /TestFolder/TestArticle, switch language to "fre"
• Access the site using /TestFolder/TestArticle, switch language to "por"
• Access the site using /por/TestFolder/TestArticle, switch language to "eng"
  (note: switching from a module location such as /content/search should work as expected)