Layout and Save to RXN/RDF works not correctly when Multi-Tailed Arrow is on canvas without elements near tails or head, If no elements are near multi-tailed arrow, layout action should consider it as empty elements

[ivanmaslow]

Steps to Reproduce Case 1

1. Add Multi-Tailed Arrow with 3 tails:
   
2. Click on Layout

Actual behavior

• Arrow appears, Multi-Tailed Arrow is moved:
  

Expected behavior

• Multi-Tailed arrow is moved to the center and size is changed to default for indigo (Update layout for pathway reaction on canvas #2309)

3. Click one more time - multi-tailed arrow disappears, the arrow is moved to the center
   

Steps to Reproduce Case 2

1. Add Multi-Tailed Arrow with 3 tails, add benzene rings, leave two tails without elements:
   
2. Click on Layout

Actual behavior

• Arrow appears, Multi-Tailed Arrow is moved:
  

Expected behavior

• Multi-Tailed arrow is moved to the center with elements and size of arrow is changed to default for indigo:
  

3. Click one more time - multi-tailed arrow disappears, the arrow is moved to the center

Steps to Reproduce Case 3

1. Add Multi-Tailed Arrow with 3 tails, add elements and single arrow:
   
2. Click on Layout

Actual behavior

• Multi-Tailed Arrow disappear:
  

Expected behavior

• Multi-Tailed arrow is moved to the center with elements and size of arrow is changed to default for indigo

Environment details

• Tested on CI-CD 2237-detect-pathway SA environment
• Ketcher [Version 2.25.0-rc.2] Build at 2024-09-24; 02:30:35
• Indigo Version 1.25.0-dev.1.58-ga966745f-wasm32-wasm-clang-12.0.0
• Windows 11 Enterprise
• Chrome Version 129.0.6668.59 (Official Build) (64-bit)

Notes

• Test cases are added to xls for RDF, RXN and Layout and should be automated
• This fix is affected save to RXN/RDF as well, for example a case with Cascade reaction:
  1. Add a reaction from the KET file:
     1-cascade-branches-ordering.zip
  2. Add an additional tail to any multi-tailed arrow:
     
  3. Click on save to RDF - there is a 6:4 reaction that's not correct, all elements shouldn't be united:
     
• Issue is detected during exploratory testing of Import/Export of Multi-Tailed Arrow in cascade reactions - Import/export multi-tails in KET #2236