fix(AdminController): Catch failed cpuinfo readfile

fixes #964

Signed-off-by: Marcel Klehr <[email protected]>

lib/Controller/AdminController.php

@@ -151,7 +151,7 @@ public function avx(): JSONResponse {
 		} catch (\Throwable $e) {
 			return new JSONResponse(['avx' => null]);
 		}
-		return new JSONResponse(['avx' => strpos($cpuinfo, 'avx') !== false]);
+		return new JSONResponse(['avx' => $cpuinfo !== false && strpos($cpuinfo, 'avx') !== false]);
 	}
 
 	public function platform(): JSONResponse {