Remove duplicate routine_address == 0 check from op_call

The _call() method already handles this case, so the check in op_call is redundant.

src/mudlib/zmachine/zcpu.py

@@ -605,17 +605,7 @@ class ZCpu:
     # call in v1-3
     def op_call(self, routine_addr, *args):
         """Call the routine r1, passing it any of r2, r3, r4 if defined."""
-        # Calling address 0 is a no-op that returns false (0).
-        if routine_addr == 0:
-            self._write_result(0)
-            return
-        addr = self._memory.packed_address(routine_addr)
-        return_addr = self._opdecoder.get_store_address()
-        current_addr = self._opdecoder.program_counter
-        new_addr = self._stackmanager.start_routine(
-            addr, return_addr, current_addr, args
-        )
-        self._opdecoder.program_counter = new_addr
+        self._call(routine_addr, args, True)
 
     def op_call_vs(self, routine_addr, *args):
         """See op_call."""