Add allocation checks for accumulating history variables.

[dabail10]

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PR checklist

• Short (1 sentence) summary of your PR:
  Add allocated checks for accumulation of history variables.
• Developer(s):
  D. Bailey (dabail10)
• Suggest PR reviewers from list in the column to the right.
• Please copy the PR test results link or provide a summary of testing completed below.
  I have run this for a month with daily and monthly output on cheyenne_intel.
• How much do the PR code changes differ from the unmodified code?
  • bit for bit
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on Icepack or any other models?
  • Yes
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/. A test build of the technical docs will be performed as part of the PR testing.)
  • Yes
  • No, does the documentation need to be updated at a later time?
    • Yes
    • No
• Please provide any additional information or relevant details below:
  This is a fix for issue Unelegant crash writing initial condition when 'histfreq' is more frequent then any 'f_*' output variable #521 raised by @phil-blain . The fix is to check that the a2D, a3Dc, etc. arrays are allocated before doing the accumulation. Also, print a warning if there are no fields going to the history. Also added some spaces in ice_history_bgc.F90. Some the lines did not start in column 6.

[eclare108213]

Looks good to me. I wouldn't have worried about the column-6 alignment but this is fine.

[apcraig]

This looks fine to me. Maybe @phil-blain could test this modification?

The review button isn't working at the moment for some reason, it looks like they changed a few things around on github and maybe there is a bug. I'll check to see if it works for me later.

[phil-blain]

Thanks @dabail10. I tested this with the same ice_in as in #521 and it does not crash, and "WARNING: NO HISTORY FIELDS WILL BE WRITTEN" is written to the log file as expected.

The fix is simple and effective.