Prevent panic on requests with invalid URIs

When `try_into_http_request` was used with an invalid base URI the code
was panicking. Acording to `http::request::Builder` documentation,
`headers_mut` returns `None` if the builder contains errors, which was
the case when an invalid URI was provided.

The new version only sets the additional headers in case that there are
no errors on the builder, preventing the panic. The conversion will
return an error when the builder is consumed on `body`.

crates/ruma-api-macros/src/api/request/outgoing.rs

@@ -226,11 +226,9 @@ impl Request {
                             "application/json",
                         );
 
-                    let mut req_headers = req_builder
+                    if let Some(mut req_headers) = req_builder.headers_mut() {
-                        .headers_mut()
+                        #header_kvs
-                        .expect("`http::RequestBuilder` is in unusable state");
+                    }
-
-                    #header_kvs
 
                     let http_request = req_builder.body(#request_body)?;
 

crates/ruma-api/CHANGELOG.md

@@ -21,6 +21,10 @@ Improvements:
 * Add a new `MatrixError` type to the `error` module that consists of a HTTP status code and JSON
   `body` and is the new default error type for `ruma_api!`
 
+Bug fixes:
+
+* Prevent panic when building requests with an invalid URI  
+
 # 0.16.1
 
 Bug fixes:

crates/ruma-api/tests/conversions.rs

@@ -62,6 +62,21 @@ fn request_serde() {
     assert_eq!(req.user, req2.user);
 }
 
+#[test]
+fn invalid_uri_should_not_panic() {
+    let req = Request {
+        hello: "hi".to_owned(),
+        world: "test".to_owned(),
+        q1: "query_param_special_chars %/&@!".to_owned(),
+        q2: 55,
+        bar: "barVal".to_owned(),
+        user: user_id!("@bazme:ruma.io"),
+    };
+
+    let result = req.clone().try_into_http_request::<Vec<u8>>("invalid uri", SendAccessToken::None);
+    assert!(result.is_err());
+}
+
 #[test]
 fn request_with_user_id_serde() {
     let req = Request {