Edit profile fixes (#258)

* Fix: only clear banner or avi when requested in edit profile

* Set the default snap points to 90% to ensure the modal never fails to raise

src/state/models/profile-view.ts

@@ -146,7 +146,7 @@ export class ProfileViewModel {
         cid: res.data.cid,
         mimeType: newUserAvatar.mime,
       }
-    } else {
+    } else if (newUserAvatar === null) {
       updates.avatar = null
     }
     if (newUserBanner) {
@@ -159,7 +159,7 @@ export class ProfileViewModel {
         cid: res.data.cid,
         mimeType: newUserBanner.mime,
       }
-    } else {
+    } else if (newUserBanner === null) {
       updates.banner = null
     }
     await this.rootStore.api.app.bsky.actor.updateProfile(updates)