Quit when there are no properties to verify

We give a "vacuous" successful message

Author: lou1306

backends.py

@@ -163,6 +163,9 @@ def simulate(self, fname, info, simulate):
     def verify(self, fname, info):
         """Verifies the correctness of the program at fname.
         """
+        if self.kwargs.get("no_properties") or not info.properties:
+            log.info("No property to verify!")
+            return ExitStatus.SUCCESS
         args = self.debug_args if self.kwargs["debug"] else self.args
         cmd = [self.command, *self.filename_argument(fname), *args]
         if self.kwargs.get("timeout", 0) > 0:
@@ -321,6 +324,9 @@ def check_cadp(self):
     def verify(self, fname, info):
         if not(self.check_cadp()):
             return ExitStatus.BACKEND_ERROR
+        if self.kwargs.get("no_properties") or not info.properties:
+            log.info("No property to verify!")
+            return ExitStatus.SUCCESS
         modality = info.properties[0].split()[0]
         mcl = "fairly.mcl" if modality == "finally" else "never.mcl"
         mcl = str(Path("cadp") / Path(mcl))
@@ -405,6 +411,9 @@ def _mcl_fname(self, fname):
     def verify(self, fname, info):
         if not(self.check_cadp()):
             return ExitStatus.BACKEND_ERROR
+        if self.kwargs.get("no_properties") or not info.properties:
+            log.info("No property to verify!")
+            return ExitStatus.SUCCESS
         mcl = translate_property(info)
         mcl_fname = self._mcl_fname(fname)
         log.debug(f"Writing MCL query to {mcl_fname}...")