Update JNIEnvInit.cs

Author: jonathanpeppers

src/Mono.Android/Android.Runtime/JNIEnvInit.cs

@@ -77,7 +77,13 @@ static Type TypeGetType (string typeName) =>
 			JniType.GetCachedJniType (ref jniType, className);
 
 			ReadOnlySpan<char> methods = new ReadOnlySpan<char> ((void*) methods_ptr, methods_len);
-			androidRuntime!.TypeManager.RegisterNativeMembers (jniType, type, methods);
+			if (androidRuntime!.TypeManager is AndroidTypeManager typeManager) {
+				// Span-based overload
+				typeManager.RegisterNativeMembers (jniType, type, methods);
+			} else {
+				// String-based overload
+				androidRuntime!.TypeManager.RegisterNativeMembers (jniType, type, methods);
+			}
 		}
 
 		// NOTE: should have different name than `Initialize` to avoid: