bootstrap 5 template function complete

current status:
- got expiration and format selections to work
- fixed modals (password, QR-code, etc.)
- replaced glyphicons with Bootstrap icons (needs CSP relaxation to work)
- tested the different settings and combinations
- got editor tabs to change active status

to be done:
- add "Dark Mode" to translation strings
- figure out how to change prettify theme when dark mode gets selected
- check tab alignment in HTML source

lib/Controller.php

@@ -114,7 +114,7 @@ class Controller
             error_log(I18n::_('%s requires php %s or above to work. Sorry.', I18n::_('PrivateBin'), self::MIN_PHP_VERSION));
             return;
         }
-        if (strlen(PATH) < 0 && substr(PATH, -1) !== DIRECTORY_SEPARATOR) {
+        if (!empty(PATH) && substr(PATH, -1) !== DIRECTORY_SEPARATOR) {
             error_log(I18n::_('%s requires the PATH to end in a "%s". Please update the PATH in your index.php.', I18n::_('PrivateBin'), DIRECTORY_SEPARATOR));
             return;
         }
@@ -320,10 +320,10 @@ class Controller
             $this->_error = $e->getMessage();
         }
         if ($this->_request->isJsonApiCall()) {
-            if (strlen($this->_error)) {
-                $this->_return_message(1, $this->_error);
-            } else {
+            if (empty($this->_error)) {
                 $this->_return_message(0, $dataid);
+            } else {
+                $this->_return_message(1, $this->_error);
             }
         }
     }