The SVN url has been changed by SourceForge. In your repository root, or in an individual module, run the command:
svn switch --relocate https://apertium.svn.sourceforge.net/svnroot/apertium/ https://svn.code.sf.net/p/apertium/svn/

From Apertium

When you have a problem in the dictionaries, or transfer that you can't seem to fix, here is some advice to try and solve it:

[edit] Dictionaries

Make sure there are no empty elements <l></l> (also <l/>) or <r></r> (also <r/>) inside paradigms or entries in the main section.

Make sure too that no entry begins or ends with a white space (<b/>).

[edit] See also

• Bugzilla
• lttoolbox