Add asserts and whitespace fix

src/bsonc.rs

@@ -96,10 +96,12 @@ impl Bsonc {
     }
 
     pub fn inner(&self) -> *const bindings::bson_t {
+        assert!(!self.inner.is_null());
         self.inner
     }
 
     pub fn mut_inner(&mut self) -> *mut bindings::bson_t {
+        assert!(!self.inner.is_null());
         self.inner as *mut bindings::bson_t
     }
 }

src/collection.rs

@@ -162,7 +162,7 @@ impl<'a> Collection<'a> {
                 },
                 match options.read_prefs {
                     Some(ref prefs) => prefs.inner(),
-                    None        => ptr::null()
+                    None            => ptr::null()
                 },
                 error.mut_inner()
             )