Fixed the same error as previous commit in another part of the code

Author: mesonepigreco

Modules/Cluster.py

@@ -835,8 +835,16 @@ def run_atoms(self, ase_calc, ase_atoms, label="ESP",
 
         # Append the additional parameters
         for add_parameter in self.custom_params:
-            submission += "#{} --{}={}\n".format(self.submit_name, add_parameter, self.custom_params[add_parameter])
-        
+
+            adder_string = "--{}".format(add_parameter)
+            if add_parameter.startswith("-"):
+                adder_string = add_parameter
+
+            if self.custom_params[add_parameter] is None:
+                submission += "#{} {}\n".format(self.submit_name, adder_string)
+            else:
+                submission += "#{} {}={}\n".format(self.submit_name, adder_string, self.custom_params[add_parameter])
+
         # Add the loading of the modules
         submission += self.load_modules + "\n"