Allow negative car blocking numbers

[DanielBoudreau]

No description provided.

[mergeable]

Thanks for the PR. Please consider adding a release note in the help/en/releasenotes/current-draft-note.shtml file.

[codecov]

Codecov Report

Merging #9871 (f5404bd) into master (8c5201e) will increase coverage by 0.1%.
The diff coverage is 79.0%.

@@             Coverage Diff             @@
##             master    #9871     +/-   ##
===========================================
+ Coverage      51.8%    51.8%   +0.1%     
- Complexity    64095    64115     +20     
===========================================
  Files          5099     5099             
  Lines        445244   445238      -6     
  Branches      64342    64336      -6     
===========================================
+ Hits         230199   230264     +65     
+ Misses       192302   192230     -72     
- Partials      22743    22744      +1     

Impacted Files	Coverage Δ
...ri/jmrit/operations/rollingstock/RollingStock.java	81.0% <ø> (ø)
...operations/rollingstock/RollingStockEditFrame.java	94.4% <20.0%> (-0.2%)	⬇️
...src/jmri/jmrit/operations/trains/TrainBuilder.java	94.2% <100.0%> (+0.5%)	⬆️
.../jmrit/symbolicprog/tabbedframe/WatchingLabel.java	38.5% <0.0%> (-15.3%)	⬇️
...54/xbee/swing/nodeconfig/AssignmentTableModel.java	20.5% <0.0%> (-14.2%)	⬇️
...ri/jmrit/operations/routes/tools/ExportRoutes.java	67.9% <0.0%> (-8.3%)	⬇️
java/src/jmri/jmris/JmriConnection.java	59.0% <0.0%> (-7.6%)	⬇️
java/src/jmri/server/json/JsonWebSocket.java	46.7% <0.0%> (-6.6%)	⬇️
java/src/jmri/jmrit/entryexit/PointDetails.java	36.6% <0.0%> (-5.7%)	⬇️
...ix/can/cbus/swing/nodeconfig/CbusNodeInfoPane.java	79.1% <0.0%> (-4.1%)	⬇️
... and 38 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8c5201e...f5404bd. Read the comment docs.

[coveralls]

Coverage increased (+0.02%) to 56.884% when pulling f5404bd on DanielBoudreau:master into 8c5201e on JMRI:master.