Allow to delete process without having had edges

[swaterkamp]

What:
For a new process map it was not possible to delete a process without having had an edge created first. BPM crashed in that case. The crash now no longer happens.

Why:
To fix above mentioned bug

How:
Created a new user and go to BPM. Created a process and no edge. Deleted that process and saw BPM not crash.
An automated test was not written for this functionality, because it would only be possible to get an very indirect test at best.

Checklist:

• [N/A] Tests
• CHANGELOG Entry

[codecov]

Codecov Report

Merging #2507 into gsa-20.08 will increase coverage by 0.30%.
The diff coverage is 76.38%.

@@              Coverage Diff              @@
##           gsa-20.08    #2507      +/-   ##
=============================================
+ Coverage      52.76%   53.07%   +0.30%     
=============================================
  Files           1070     1072       +2     
  Lines          25789    25892     +103     
  Branches        7312     7397      +85     
=============================================
+ Hits           13607    13741     +134     
+ Misses         11058    11029      -29     
+ Partials        1124     1122       -2     

Impacted Files	Coverage Δ
gsa/src/gmp/commands/wizard.js	9.23% <0.00%> (ø)
gsa/src/gmp/models/tlscertificate.js	100.00% <ø> (ø)
gsa/src/web/components/error/errorpanel.js	100.00% <ø> (ø)
gsa/src/web/pages/alerts/dialog.js	20.33% <ø> (ø)
gsa/src/web/pages/cpes/details.js	11.11% <ø> (ø)
gsa/src/web/pages/extras/trashactions.js	5.49% <0.00%> (ø)
gsa/src/web/pages/hosts/dialog.js	50.00% <ø> (ø)
gsa/src/web/pages/policies/detailspage.js	100.00% <ø> (ø)
gsa/src/web/pages/policies/row.js	100.00% <ø> (ø)
gsa/src/web/pages/portlists/detailspage.js	34.48% <ø> (ø)
... and 64 more

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