fix for non similarity sss

Resolves #<>

Describe the change in few words here

• This change has security impacts (if so, add them to the description)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (README, Confluence etc.)
• My changes generate no new warnings in the build
• I have added tests that prove my fix is effective or that my feature works
• My code does not decrease pylint score

Dependencies

• This Merge Request is dependent on any other Merge Request or configuration or some ticket; please mention here
• Includes migration
• Installs new requirement

Post Review

• Squash and merge feature_branch to staging
• Delete branch after merge

Additional Description

Add any extra details needed for this PR.

api/public/views/elastic_search.py

@@ -218,7 +218,9 @@ class StructureSearchAPI(AdvancedSearchAPIBAse):
     def get(self, request):
         smiles = self.request.query_params.get("smiles", None)
         search_type = self.request.query_params.get("search_type", None)
-        similarity = float(self.request.query_params.get("similarity", None))
+        similarity = self.request.query_params.get("similarity", None)
+        if similarity is not None:
+            similarity = float(similarity)
         structure_search = FullSpecification(
             structure_search=StructureSearch(structure=smiles, type=search_type, similarity=similarity)
         )