No longer raising a missing parameter when value is null

When passing a null value as parameter (ex.: 0, None or False), Sanic said "Error: Required parameter `param` was not passed to url_for"

Example:

```
@app.route("/<idx>")
def route(rq, idx):
    pass
```

```
url_for("route", idx=0)
```

No longer raises: `Error: Required parameter `idx` was not passed to url_for`

sanic/app.py

@@ -495,7 +495,7 @@ class Sanic:
             specific_pattern = '^{}$'.format(pattern)
             supplied_param = None
 
-            if kwargs.get(name):
+            if name in kwargs:
                 supplied_param = kwargs.get(name)
                 del kwargs[name]
             else: