Core: Fix undefined behavior in mem_map_funcs' WriteBlock function

src/core/mem_map_funcs.cpp

@@ -289,11 +289,15 @@ void Write64(const u32 addr, const u64 data) {
 
 void WriteBlock(const u32 addr, const u8* data, const int size) {
     int offset = 0;
-    while (offset < (size & ~3))
-        Write32(addr + offset, *(u32*)&data[offset += 4]);
+    while (offset < (size & ~3)) {
+        Write32(addr + offset, *(u32*)&data[offset]);
+        offset += 4;
+    }
 
-    if (size & 2)
-        Write16(addr + offset, *(u16*)&data[offset += 2]);
+    if (size & 2) {
+        Write16(addr + offset, *(u16*)&data[offset]);
+        offset += 2;
+    }
 
     if (size & 1)
         Write8(addr + offset, data[offset]);