Empty 'percent_change' in get_ticker API

[Zapata]

Bug Description

Following release 2.0.190219 the 'percent_change' field is empty in the get_ticker API when there is no value change (should be 0).

Impacts

• API (the application programming interface)
• Build (the build process or something prior to compiled code)
• CLI (the command line wallet)
• Deployment (the deployment process after building such as Docker, Travis, etc.)
• DEX (the Decentralized EXchange, market engine, etc.)
• P2P (the peer-to-peer network for transaction/block propagation)
• Performance (system or user efficiency, etc.)
• Protocol (the blockchain logic, consensus, validation, etc.)
• Security (the security of system or user data, etc.)
• UX (the User Experience)
• Other (please add below)

Steps To Reproduce

curl -s --data '{"jsonrpc": "2.0", "method": "call", "params": [0, "get_ticker", ["RUBLE", "USD"]], "id": 1}' https://node.bitshares.eu/ | jq
{
  "id": 1,
  "jsonrpc": "2.0",
  "result": {
    "time": "2019-02-27T11:01:12",
    "base": "RUBLE",
    "quote": "USD",
    "latest": "68.96551724137931034482",
    "lowest_ask": "68",
    "highest_bid": "56.00518806744487678339",
    "percent_change": "",
    "base_volume": "0",
    "quote_volume": "0"
  }
}

Note that the node is running 2.0.190219 version.

Expected Behavior

curl -s --data '{"jsonrpc": "2.0", "method": "call", "params": [0, "get_ticker", ["RUBLE", "USD"]], "id": 1}' https://api.dex.trading/ | jq
{
  "id": 1,
  "jsonrpc": "2.0",
  "result": {
    "time": "2019-02-27T11:01:12",
    "base": "RUBLE",
    "quote": "USD",
    "latest": "68.96551724137931034482",
    "lowest_ask": "68",
    "highest_bid": "56.00518806744487678339",
    "percent_change": "0",
    "base_volume": "0",
    "quote_volume": "0"
  }
}

Note that the node is running a previous version 2.0.181221.

Host Environment
Version: 2.0.190219

CORE TEAM TASK LIST

• Evaluate / Prioritize Bug Report
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
• Perform QA/Testing
• Update Documentation

[Zapata]

Bug introduced by #842 / PR #1549 , a missing else there I suppose .

[oxarbitrage]

Thanks @Zapata , i think initializing in the top around: https://github.com/oxarbitrage/bitshares-core/blob/04f20af8333390416944e602c0380315ca4f7a88/libraries/app/database_api.cpp#L324 will do it.

Something like:

percent_change = "0";

Now i am wondering if this is important enough to go into the release branch and direct way to master now in form of hotfix.

Opinions?

[pmconrad]

Since it breaks (some) clients we should create a hotfix release IMO.