Check for empty result in Modify shell files

CHANGELOG.md

@@ -47,6 +47,7 @@ Changelog](https://keepachangelog.com/en/1.0.0/).
 - Encryptor breaking with UTF-8 characters. (Passwords in different languages can be submitted in
   the config successfully now.) #1490
 - Mimikatz collector no longer fails if Azure credential collector is disabled. #1512 #1493
+- Unhandled error when "modify shell startup files PBA" is unable to find regular users. #1507
 
 
 ### Security

monkey/infection_monkey/post_breach/actions/modify_shell_startup_files.py

@@ -20,6 +20,13 @@ def __init__(self):
 
     def run(self):
         results = [pba.run() for pba in self.modify_shell_startup_PBA_list()]
+        if not results:
+            results = [
+                (
+                    "Modify shell startup files PBA failed: Unable to find any regular users",
+                    False,
+                )
+            ]
         PostBreachTelem(self, results).send()
 
     def modify_shell_startup_PBA_list(self):
@@ -61,6 +68,7 @@ def run(self):
                         output = subprocess.check_output(  # noqa: DUO116
                             self.command, stderr=subprocess.STDOUT, shell=True
                         ).decode()
+
                         return output, True
                     except subprocess.CalledProcessError as e:
                         # Return error output of the command