Simplify arig and aseq buffer base calculation

Just use the size of the arig guid ref buffer to determine the base of the aseq guid ref buffer. This simplification reduces the chances of bugs like 5771b7c

src/assets/model.cpp

@@ -114,7 +114,6 @@ static void Model_AllocateIntermediateDataChunk(CPakFileBuilder* const pak, PakP
     if (hasGuidRefs)
     {
         asset.ExpandGuidBuf(animrigCount + sequenceCount);
-        uint64_t curIndex = 0;
 
         if (animrigRefs)
         {
@@ -132,13 +131,12 @@ static void Model_AllocateIntermediateDataChunk(CPakFileBuilder* const pak, PakP
                 const PakGuid_t guid = *reinterpret_cast<PakGuid_t*>(&intermediateChunk.data[offset]);
 
                 Pak_RegisterGuidRefAtOffset(guid, offset, intermediateChunk, asset);
-                curIndex++;
             }
         }
 
         if (sequenceRefs)
         {
-            const size_t base = alignedNameBufLen + (curIndex * sizeof(PakGuid_t));
+            const size_t base = alignedNameBufLen + animRigRefsBufLen;
 
             memcpy(&intermediateChunk.data[base], sequenceRefs, sequenceRefsBufLen);
             delete[] sequenceRefs;