powershell - OR operator for checking branches in Octopus Deploy -

i have 'deploy nuget package' step in octopus. in step, want deploy nuget package , have deployment script executed.

now want deployment happen master , hotfix branches.so added condition in deployemnt script:

 if ($branchname.tolower().equals("master") -or $branchname.tolower().contains("hotfix"))   {   ...................  } 

but doesn't work , gettin error

 'you cannot call method on null-valued expression.' 

how can achieve this?

note: don't have pre-deployment , post-deployment script

are able check if $branchname null? can compare strings inbuilt operators:

if ($branchname -and ($branchname -ilike "master" -or $branchname -ilike "*hotfix*"))  {   ...................  }