Merge topic 'ExternalProject-svn-auth-blank'

ecd11a2 ExternalProject: Allow blank SVN_USERNAME/SVN_PASSWORD (#14128)

Modules/ExternalProject.cmake

@@ -1251,10 +1251,10 @@ function(_ep_add_download_command name)
     get_filename_component(work_dir "${source_dir}" PATH)
     set(comment "Performing download step (SVN checkout) for '${name}'")
     set(svn_user_pw_args "")
-    if(svn_username)
+    if(DEFINED svn_username)
       set(svn_user_pw_args ${svn_user_pw_args} "--username=${svn_username}")
     endif()
-    if(svn_password)
+    if(DEFINED svn_password)
       set(svn_user_pw_args ${svn_user_pw_args} "--password=${svn_password}")
     endif()
     if(svn_trust_cert)
@@ -1473,10 +1473,10 @@ function(_ep_add_update_command name)
     get_property(svn_password TARGET ${name} PROPERTY _EP_SVN_PASSWORD)
     get_property(svn_trust_cert TARGET ${name} PROPERTY _EP_SVN_TRUST_CERT)
     set(svn_user_pw_args "")
-    if(svn_username)
+    if(DEFINED svn_username)
       set(svn_user_pw_args ${svn_user_pw_args} "--username=${svn_username}")
     endif()
-    if(svn_password)
+    if(DEFINED svn_password)
       set(svn_user_pw_args ${svn_user_pw_args} "--password=${svn_password}")
     endif()
     if(svn_trust_cert)