Getting System Error page when accessing Application Links page and User Language setting is set to Polish

Steps to Reproduce

1. Install Confluence-5.0.1-language-pack-pl_PL.jar (from https://translations.atlassian.com/)
2. Set the Global Default Language (http://Confluence-URL/admin/viewlanguage.action) to "polski (Polska)"
3. Go to http://Confluence-URL/users/viewmysettings.action
4. Change the Language to "polski (Polska)"
5. Go to Browse >> Confluence Admin >> Application Links. Or just simply access http://Confluence-URL/admin/listapplicationlinks.action.
6. You'll get a System Error page with the following stack trace in the log:

   2013-03-07 15:27:53,372 ERROR [http-8041-3] [atlassian.confluence.servlet.ConfluenceServletDispatcher] sendError Could not execute action
    -- url: /confluence/spaces/listentitylinks.action | userName: admin | referer: http://localhost:8041/confluence/spaces/editspace.action?key=SEVT
   org.apache.velocity.exception.MethodInvocationException: Invocation of method 'getLink' in  class com.atlassian.applinks.core.docs.DocumentationLinkerImpl threw exception java.lang.RuntimeException: Failed to concatenate http://confluence.atlassian.com/display/APPLINKS to form URI (Illegal character in path) at /common/_help_link.vm[line 11, column 87]
   	at org.apache.velocity.runtime.parser.node.ASTMethod.handleInvocationException(ASTMethod.java:337)
   	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:284)
   	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:262)
   	at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:342)
   	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
   	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:336)
   	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:106)
   	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
   .
   .
   .
   Caused by: java.lang.RuntimeException: Failed to concatenate http://confluence.atlassian.com/display/APPLINKS to form URI (Illegal character in path)
   	at com.atlassian.applinks.core.util.URIUtil.uncheckedConcatenate(URIUtil.java:118)
   	at com.atlassian.applinks.core.docs.DocumentationLinkerImpl.getLink(DocumentationLinkerImpl.java:34)
   	at com.atlassian.applinks.core.docs.DocumentationLinkerImpl.getLink(DocumentationLinkerImpl.java:24)
   	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   	at java.lang.reflect.Method.invoke(Method.java:597)
   	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:389)
   	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:378)
   	at com.atlassian.confluence.velocity.introspection.UnboxingMethod.invoke(UnboxingMethod.java:33)
   	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:270)
   	... 230 more
   Caused by: java.net.URISyntaxException: Illegal character in path at index 61: http://confluence.atlassian.com/display/APPLINKS/Przychodz?ce + i + wychodz?cej + uwierzytelniania
   	at java.net.URI$Parser.fail(URI.java:2809)
   	at java.net.URI$Parser.checkChars(URI.java:2982)
   	at java.net.URI$Parser.parseHierarchical(URI.java:3066)
   	at java.net.URI$Parser.parse(URI.java:3014)
   	at java.net.URI.<init>(URI.java:578)
   	at com.atlassian.applinks.core.util.URIUtil.concatenate(URIUtil.java:28)
   	at com.atlassian.applinks.core.util.URIUtil.uncheckedConcatenate(URIUtil.java:114)
   	... 240 more
   

7. Same error observed when accessing Space Admin >> Application Links

This issue is related to this fixed bug: CONF-24172. The problem is only observed when Polish Language Pack is in used. German Language Pack is not affected.

Workaround

Set your language setting temporarily to English through http://Confluence-URL/users/viewmysettings.action and do the necessary changes in Application Link page.