fix(plugins): improve type checking for structured output

- Split type checking into two separate conditions for clarity
- Add early return when output contains non-string objects
- Ensure structured output like MikrotikBGPRouteTable passes through unchanged
- Prevent AttributeError on .strip() for tuple containing structured data

Resolves remaining crashes when processing already-structured BGP route data.

hyperglass/plugins/_builtin/mikrotik_garbage_output.py

@@ -99,13 +99,17 @@ class MikrotikGarbageOutput(OutputPlugin):
         """
 
         # If output is already processed/structured (not raw strings), pass it through unchanged
-        if not isinstance(output, (tuple, list)) or (output and not isinstance(output[0], str)):
+        if not isinstance(output, (tuple, list)):
+            return output
+            
+        # Check if the tuple/list contains non-string objects (structured data)
+        if output and not isinstance(output[0], str):
             return output
 
         cleaned_outputs = []
 
         for raw_output in output:
-            # Handle non-string outputs (already processed by other plugins)
+            # Handle non-string outputs (already processed by other plugins) - double check
             if not isinstance(raw_output, str):
                 cleaned_outputs.append(raw_output)
                 continue