[3.10] Dont show the pre upgrade checker when the upgrade is not supported

[jgerman-bot]

New language relevant PR in upstream repo: joomla/joomla-cms#36312 Here are the upstream changes:

Click to expand the diff!

diff --git a/administrator/components/com_joomlaupdate/views/default/view.html.php b/administrator/components/com_joomlaupdate/views/default/view.html.php
index c64170864a42..e2d896ef0dbf 100644
--- a/administrator/components/com_joomlaupdate/views/default/view.html.php
+++ b/administrator/components/com_joomlaupdate/views/default/view.html.php
@@ -268,6 +268,12 @@ private function checkForSelfUpdate()
 	 */
 	public function shouldDisplayPreUpdateCheck()
 	{
+		// When the download URL is not found there is no core upgrade path
+		if (!isset($this->updateInfo['object']->downloadurl->_data))
+		{
+			return false;
+		}
+
 		$nextMinor = JVersion::MAJOR_VERSION . '.' . (JVersion::MINOR_VERSION + 1);
 
 		// Show only when we found a download URL, we have an update and when we update to the next minor or greater.
diff --git a/administrator/language/en-GB/en-GB.com_joomlaupdate.ini b/administrator/language/en-GB/en-GB.com_joomlaupdate.ini
index 336beaf3b3c4..36eabd0859a0 100644
--- a/administrator/language/en-GB/en-GB.com_joomlaupdate.ini
+++ b/administrator/language/en-GB/en-GB.com_joomlaupdate.ini
@@ -109,7 +109,7 @@ COM_JOOMLAUPDATE_VIEW_DEFAULT_METHOD_FTP="Write files using FTP"
 COM_JOOMLAUPDATE_VIEW_DEFAULT_METHOD_HYBRID="Hybrid (use FTP only if needed)"
 COM_JOOMLAUPDATE_VIEW_DEFAULT_NOUPDATES="No updates available."
 COM_JOOMLAUPDATE_VIEW_DEFAULT_NOUPDATESNOTICE="You already have the latest Joomla version, %s."
-COM_JOOMLAUPDATE_VIEW_DEFAULT_NO_DOWNLOAD_URL="We can't find a download URL"
+COM_JOOMLAUPDATE_VIEW_DEFAULT_NO_DOWNLOAD_URL="Update unavailable"
 COM_JOOMLAUPDATE_VIEW_DEFAULT_NO_DOWNLOAD_URL_DESC="An update to Joomla %1$s was found, but it wasn't possible to download that update. There are three possibilities why this happens:<br>- Your host doesn't support <a href="_QQ_"https://downloads.joomla.org/technical-requirements"_QQ_">the minimum requirements for Joomla %1$s</a> and there is no alternative download for your configuration available.<br>- The update to Joomla %1$s is not available for your stability level.<br>- There is a problem with the Joomla Update Server.<br><br>Please try to download the update package from <a href="_QQ_"https://downloads.joomla.org/latest"_QQ_">the official Joomla download page</a> and use the Upload and Update tab."
 COM_JOOMLAUPDATE_VIEW_DEFAULT_NO_LIVE_UPDATE="A new version of the Joomla Update Component is available."
 COM_JOOMLAUPDATE_VIEW_DEFAULT_NO_LIVE_UPDATE_DESC="You must update this first before you can update Joomla! <a class=\"alert-link\" href="_QQ_"index.php?option=com_installer&view=update"_QQ_">Click here to update the component</a>."