Toml doesnt support None (#101)

Replaced None value with blank str

dex_starr/settings.py

@@ -8,7 +8,7 @@
 ]
 
 from pathlib import Path
-from typing import ClassVar, List, Optional
+from typing import ClassVar, List
 
 from pydantic import BaseModel, Extra, Field, validator
 
@@ -31,23 +31,23 @@ class Config:
 
 class MetronSettings(SettingsModel):
     generate_metroninfo_file: bool = True
-    password: Optional[str] = None
-    username: Optional[str] = None
+    password: str = ""
+    username: str = ""
 
 
 class MarvelSettings(SettingsModel):
-    public_key: Optional[str] = None
-    private_key: Optional[str] = None
+    public_key: str = ""
+    private_key: str = ""
 
 
 class LeagueOfComicGeeksSettings(SettingsModel):
-    client_id: Optional[str] = None
-    client_secret: Optional[str] = None
-    access_token: Optional[str] = None
+    client_id: str = ""
+    client_secret: str = ""
+    access_token: str = ""
 
 
 class ComicvineSettings(SettingsModel):
-    api_key: Optional[str] = None
+    api_key: str = ""
 
 
 class GeneralSettings(SettingsModel):
@@ -66,7 +66,7 @@ def validate_output_format(cls, v):
 
 
 class Settings(SettingsModel):
-    FILENAME: ClassVar = get_config_root() / "settings.toml"
+    FILENAME: ClassVar[str] = get_config_root() / "settings.toml"
     general: GeneralSettings = GeneralSettings(
         resolution_order=[
             "Marvel",