[BUGFIX] Prevent extension download if disabled

If you disable extension installation in Install Tool (disable all
[EXT][allow*Install] options) a weird error is thrown if you try to
install an extension anyway. This patch hides the "Import and Install"
button of no install path is available.

Resolves: #58800
Releases: master, 6.2
Change-Id: I057e7e4d6a8360638c60427b3855142ab7df2147
Reviewed-on: http://review.typo3.org/38093


Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>

typo3/sysext/extensionmanager/Classes/ViewHelpers/DownloadExtensionViewHelper.php

@@ -37,6 +37,9 @@ class DownloadExtensionViewHelper extends \TYPO3\CMS\Fluid\ViewHelpers\FormViewH
 	 */
 	public function render(\TYPO3\CMS\Extensionmanager\Domain\Model\Extension $extension) {
 		$installPaths = \TYPO3\CMS\Extensionmanager\Domain\Model\Extension::returnAllowedInstallPaths();
+		if (empty($installPaths)) {
+			return '';
+		}
 		$pathSelector = '<ul class="is-hidden">';
 		foreach ($installPaths as $installPathType => $installPath) {
 			$pathSelector .= '<li>