add check for default config file

slither/__main__.py

@@ -462,7 +462,7 @@ def parse_args(detector_classes, printer_classes):  # pylint: disable=too-many-s
         help="Provide a config file (default: slither.config.json)",
         action="store",
         dest="config_file",
-        default="slither.config.json",
+        default=None,
     )
 
     group_misc.add_argument(

slither/utils/command_line.py

@@ -52,6 +52,12 @@ defaults_flag_in_config = {
 
 
 def read_config_file(args):
+    # No config file was provided as an argument
+    if args.config_file == None:
+        # Check wether the default config file is present
+        if not os.path.exists("slither.config.json"):
+            return
+
     if os.path.isfile(args.config_file):
         try:
             with open(args.config_file, encoding="utf8") as f: