IL2CPP: Fix crash when loading Il2CppCodeGenModule with no concrete methods (#58)

Il2CppInspector.Common/IL2CPP/Il2CppBinary.cs

@@ -235,7 +235,14 @@ namespace Il2CppInspector
                     CodeGenModulePointers.Add(name, mp.Pointer);
 
                     // Read method pointers
+                    // If a module contains only interfaces, abstract methods and/or non-concrete generic methods,
+                    // the entire method pointer array will be NULL values, causing the methodPointer to be mapped to .bss
+                    // and therefore out of scope of the binary image
+                    try {
                         ModuleMethodPointers.Add(module, Image.ReadMappedArray<ulong>(module.methodPointers, (int) module.methodPointerCount));
+                    } catch (InvalidOperationException) {
+                        ModuleMethodPointers.Add(module, new ulong[module.methodPointerCount]);
+                    }
 
                     // Read method invoker pointer indices - one per method
                     MethodInvokerIndices.Add(module, Image.ReadMappedArray<int>(module.invokerIndices, (int) module.methodPointerCount));

Il2CppInspector.Common/Reflection/TypeModel.cs

@@ -146,6 +146,7 @@ namespace Il2CppInspector.Reflection
                 .ToDictionary(g => g.Key, g => g.GroupBy(a => a.AttributeType).Select(g => g.First()).ToList());
 
             // Create method invokers (one per signature, in invoker index order)
+            // Generic type definitions have an invoker index of -1
             foreach (var method in MethodsByDefinitionIndex) {
                 var index = package.GetInvokerIndex(method.DeclaringType.Assembly.ModuleDefinition, method.Definition);
                 if (index != -1) {
@@ -156,7 +157,6 @@ namespace Il2CppInspector.Reflection
                 }
             }
 
-            // TODO: Some invokers are not initialized or missing, need to find out why
             // Create method invokers sourced from generic method invoker indices
             foreach (var spec in GenericMethods.Keys) {
                 if (package.GenericMethodInvokerIndices.TryGetValue(spec, out var index)) {