fix run-tests.py crash when all tests are filtered
fix run-tests.py crash when all tests are filtered

WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,tclin914/sexpr-wasm-prototype-64,WebAssembly/wabt,tclin914/sexpr-wasm-prototype-64,WebAssembly/sexpr-wasm-prototype,citisolo/wabt,tclin914/sexpr-wasm-prototype-64,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,tclin914/sexpr-wasm-prototype-64,citisolo/wabt,WebAssembly/wabt,citisolo/wabt,citisolo/wabt,citisolo/wabt,WebAssembly/wabt,tclin914/sexpr-wasm-prototype-64,citisolo/wabt,WebAssembly/sexpr-wasm-prototype