- fix: NullPointerException when the config class of mod updated

- alter: better test code in `common/src/test`, `neoforge/src/test` and `fabric/src/test`, run `Test Minecraft Client(:fabric)` or `Test Minecraft Client(:neoforge)` for testing

neoforge/src/test/resources/META-INF/neoforge.mods.toml

@@ -0,0 +1,34 @@
+modLoader = "javafml"
+loaderVersion = "[2,)"
+#issueTrackerURL = ""
+license = "MIT License"
+
+[[mods]]
+modId = "modid"
+version = "${version}"
+displayName = "MidnightLib Test Mod"
+authors = "TeamMidnightDust, Motschen"
+description = '''
+Example Mod for Team MidnightDust's mods.
+'''
+
+[[dependencies.modid]]
+modId = "neoforge"
+mandatory = true
+versionRange = "[20.5,)"
+ordering = "NONE"
+side = "BOTH"
+
+[[dependencies.modid]]
+modId = "minecraft"
+mandatory = true
+versionRange = "[1.20.5,)"
+ordering = "NONE"
+side = "BOTH"
+
+[[dependencies.modid]]
+modId = "midnightlib"
+mandatory = true
+versionRange = "[1.0,)"
+ordering = "NONE"
+side = "BOTH"