[mod] auth_backend:try-catch for source-read

source/overwrites/auth_backend.php

@@ -75,9 +75,16 @@ class class_auth_backend
 						]
 					)
 				);
+				try
+				{
 					$data = $realm->source->read();
 					return ($data !== null);
 				}
+				catch (\Throwable $throwable)
+				{
+					return false;
+				}
+			}
 		}
 	}