[FIX] Default value when no value found

[diggy128]

Default value should be set to Empty record instead of False for
Many2one fields when no value is to be set.
See: odoo/odoo#4384

[anajuaristi]

Hi @diggy128. Thank you for your contribution.

@oihane @Daniel-CA
Could you please review this PR? I'm not sure it's correct since add middle staff should not show any value but let user to select the product he wants from full catalogue.

Please let me know

[oihane]

@diggy128 can you please rebase this PR?

Thanks for your contribution, let's see if the travis fixes.

[Daniel-CA]

👍 LGTM, waiting for rebase.

[codecov-io]

Codecov Report

Merging #1377 into 8.0 will decrease coverage by 14.3%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              8.0   #1377       +/-   ##
==========================================
- Coverage   61.71%   47.4%   -14.31%     
==========================================
  Files         284      25      -259     
  Lines        8556     791     -7765     
==========================================
- Hits         5280     375     -4905     
+ Misses       3276     416     -2860

Impacted Files	Coverage Δ
...lity_control_between_dates/models/qc_inspection.py	31.25% <0%> (-68.75%)	⬇️
quality_control_mrp_operations/models/mrp.py	31.11% <0%> (-63.34%)	⬇️
quality_control_samples/models/qc_inspection.py	42.85% <0%> (-52.39%)	⬇️
quality_control_version/hooks.py	50% <0%> (-50%)	⬇️
quality_control_version/models/qc_test.py	43.33% <0%> (-36.67%)	⬇️
quality_control_tolerance/models/qc_inspection.py	35% <0%> (-27.5%)	⬇️
quality_control_samples/models/qc_sample.py	63.33% <0%> (-26.67%)	⬇️
quality_control_between_dates/models/qc_test.py	39.13% <0%> (-26.09%)	⬇️
quality_control_hr/models/qc_inspection.py	83.33% <0%> (-16.67%)	⬇️
quality_control_tolerance/models/qc_test.py	50% <0%> (-14.07%)	⬇️
... and 258 more

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[diggy128]

Sorry for the mess. my zenbook's touchpad is freaking out and pissing me off.
Should be OK now.