## Issue Addressed
The PR fixes a bug where the the ideal rewards for source and head were incorrectly set.
Output from testing a validator that performed optimally in a Phase 0 epoch , note the `source` and `target` under ideal rewards is incorrect (compared to the actual `total_rewards` below):
```json
{
"ideal_rewards": [
...
{
"effective_balance": "32000000000",
"head": "18771",
"target": "18770",
"source": "18729",
"inclusion_delay": "17083",
"inactivity": "0"
}
],
"total_rewards": [
{
"validator_index": "0",
"head": "18729",
"target": "18770",
"source": "18771",
"inclusion_delay": "17083",
"inactivity": "0"
}
]
```
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