[fractal] fractal-matrix-api: Don't loop for unwrapping Option

[Alexandre Franke <afranke src gnome org>]

commit bdadb58c527506fa8c0be856e3e2578ecda7abd2
Author: Zeeshan Ali <zeenix collabora co uk>
Date:   Mon Dec 10 17:15:41 2018 +0100

    fractal-matrix-api: Don't loop for unwrapping Option
    
    Fixing clippy error:
    
    ```
    error: for loop over `dataevs.as_array()`, which is an `Option`. This is more readably written as an `if 
let` statement.
       --> fractal-matrix-api/src/util.rs:221:19
        |
    221 |         for ev in dataevs.as_array() {
        |                   ^^^^^^^^^^^^^^^^^^
        |
        = note: #[deny(clippy::for_loop_over_option)] on by default
        = help: consider replacing `for ev in dataevs.as_array()` with `if let Some(ev) = dataevs.as_array()`
        = help: for further information visit 
https://rust-lang-nursery.github.io/rust-clippy/master/index.html#for_loop_over_option
    ```
    
    Related: #370

 fractal-matrix-api/src/util.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/fractal-matrix-api/src/util.rs b/fractal-matrix-api/src/util.rs
index eb3f406..07cffed 100644
--- a/fractal-matrix-api/src/util.rs
+++ b/fractal-matrix-api/src/util.rs
@@ -218,7 +218,7 @@ pub fn get_rooms_from_json(r: &JsonValue, userid: &str, baseu: &Url) -> Result<V
 
         r.prev_batch = timeline["prev_batch"].as_str().map(|s| String::from(s));
 
-        for ev in dataevs.as_array() {
+        if let Some(ev) = dataevs.as_array() {
             for tag in ev.iter().filter(|x| x["type"] == "m.tag") {
                 if let Some(_) = tag["content"]["tags"]["m.favourite"].as_object() {
                     r.fav = true;