Fix 400 error

cc @mattwr18

What helped me to track down the problem was to compare the local
changes to master:

First, make it easy to compare with master:

1. `git fetch origin`
2. `git merge origin/master`
3. Resolve conflicts

Then track the error down:

1. `git checkout origin/master -- .`
2. `git reset`
3. Add more and more changes back and wait until the error shows up
  - `git checkout backend`
  - `git checkout webapp` bingo

See https://github.com/Human-Connection/Human-Connection/pull/237#issuecomment-481485741

webapp/store/auth.js

@@ -83,7 +83,10 @@ export const actions = {
             role
             about
             locationName
-            socialMedia
+            socialMedia {
+              id
+              url
+            }
           }
         }`)
     })