Fix delegations query in Polkadot network (#475)

* fetch delegations from stored valid. staking info

* Simplify

* Cleanup

lib/source/polkadotV0-source.js

@@ -225,29 +225,16 @@ class polkadotAPI {
     delegatorAddress,
     validatorsDictionary
   ) {
-    const api = await this.getAPI()
-    const nominations = JSON.parse(
-      JSON.stringify(await api.query.staking.nominators(delegatorAddress))
-    )
-    if (!nominations) return [] // HACK not all accounts do have nominations
-    const allNominations = nominations.reduce(
-      (all, { targets }) => all.concat(targets),
-      []
-    )
-    let delegations = allNominations
-      .map(validatorAddress => {
-        const validator = validatorsDictionary[validatorAddress]
-        if (!validator) return undefined // HACK until we load all validators
-        const nomination = validator
-          ? validator.nominations.find(({ who }) => who === delegatorAddress)
-          : undefined
-        return this.reducers.delegationReducer(
-          this.network,
-          nomination,
-          validator
-        )
+    let delegations = []
+    Object.values(validatorsDictionary).forEach(validator => {
+      validator.nominations.forEach(nomination => {
+        if (delegatorAddress === nomination.who) {
+          delegations.push(
+            this.reducers.delegationReducer(this.network, nomination, validator)
+          )
+        }
       })
-      .filter(x => !!x) //filter out not existing validators
+    })
     return delegations
   }