fix: invalid type propagation in options

Fixes #98

src/main/kotlin/app/revanced/patcher/patch/PatchOption.kt

@@ -101,11 +101,13 @@ sealed class PatchOption<T>(
      * Gets the value of the option.
      * Please note that using the wrong value type results in a runtime error.
      */
-    inline operator fun <reified V> getValue(thisRef: Any?, property: KProperty<*>) =
-        value as? V ?: throw InvalidTypeException(
+    inline operator fun <reified V> getValue(thisRef: Any?, property: KProperty<*>): V? {
+        if (value !is V?) throw InvalidTypeException(
             V::class.java.canonicalName,
             value?.let { it::class.java.canonicalName } ?: "null"
         )
+        return value as? V?
+    }
 
     /**
      * Gets the value of the option.

src/test/kotlin/app/revanced/patcher/issues/Issue98.kt

@@ -0,0 +1,18 @@
+package app.revanced.patcher.issues
+
+import app.revanced.patcher.patch.PatchOption
+import org.junit.jupiter.api.Test
+import kotlin.test.assertNull
+
+internal class Issue98 {
+    companion object {
+        var key1: String? by PatchOption.StringOption(
+            "key1", null, "title", "description"
+        )
+    }
+
+    @Test
+    fun `should infer nullable type correctly`() {
+        assertNull(key1)
+    }
+}

src/test/kotlin/app/revanced/patcher/patch/PatchOptionsTest.kt

@@ -48,7 +48,7 @@ internal class PatchOptionsTest {
 
     @Test
     fun `should return a different value when changed`() {
-        var value: String by options["key1"]
+        var value: String? by options["key1"]
         val current = value + "" // force a copy
         value = "Hello, world!"
         assertNotEquals(current, value)

src/test/kotlin/app/revanced/patcher/usage/bytecode/ExampleBytecodePatch.kt

@@ -171,32 +171,32 @@ class ExampleBytecodePatch : BytecodePatch(listOf(ExampleFingerprint)) {
     }
 
     companion object : OptionsContainer() {
-        private var key1: String by option(
+        private var key1: String? by option(
             PatchOption.StringOption(
                 "key1", "default", "title", "description", true
             )
         )
-        private var key2: Boolean by option(
+        private var key2: Boolean? by option(
             PatchOption.BooleanOption(
                 "key2", true, "title", "description" // required defaults to false
             )
         )
-        private var key3: String by option(
+        private var key3: String? by option(
             PatchOption.StringListOption(
                 "key3", "TEST", listOf("TEST", "TEST1", "TEST2"), "title", "description"
             )
         )
-        private var key4: Int by option(
+        private var key4: Int? by option(
             PatchOption.IntListOption(
                 "key4", 1, listOf(1, 2, 3), "title", "description"
             )
         )
-        private var key5: Path by option(
+        private var key5: Path? by option(
             PatchOption.PathOption(
                 "key5", File("test.txt").toPath(), "title", "description"
             )
         )
-        private var key6: String by option(
+        private var key6: String? by option(
             PatchOption.StringOption(
                 "key6", null, "title", "description", true
             )