Optimized ngx_qjs_string().

Doing JS_IsString() check first before a heavy-weight call to
JS_GetTypedArrayBuffer() which throws an exception when argument is not
a typed array.

nginx/ngx_js.c

@@ -1472,6 +1472,10 @@ ngx_qjs_string(ngx_engine_t *e, JSValueConst val, ngx_str_t *dst)
 
     cx = e->u.qjs.ctx;
 
+    if (JS_IsString(val)) {
+        goto string;
+    }
+
     buffer = JS_GetTypedArrayBuffer(cx, val, &byte_offset, &byte_length, NULL);
     if (!JS_IsException(buffer)) {
         start = JS_GetArrayBuffer(cx, &dst->len, buffer);
@@ -1492,6 +1496,8 @@ ngx_qjs_string(ngx_engine_t *e, JSValueConst val, ngx_str_t *dst)
         }
     }
 
+string:
+
     str = JS_ToCString(cx, val);
     if (str == NULL) {
         return NGX_ERROR;