Avoid UB on empty fog data record

components/esm3/fogstate.cpp

@@ -69,9 +69,9 @@ namespace ESM
             esm.getT(tex.mX);
             esm.getT(tex.mY);
 
-            size_t imageSize = esm.getSubSize() - sizeof(int) * 2;
+            const std::size_t imageSize = esm.getSubSize() - sizeof(int) * 2;
             tex.mImageData.resize(imageSize);
-            esm.getExact(&tex.mImageData[0], imageSize);
+            esm.getExact(tex.mImageData.data(), imageSize);
 
             if (dataFormat <= MaxOldForOfWarFormatVersion)
                 convertFogOfWar(tex.mImageData);
@@ -92,7 +92,7 @@ namespace ESM
             esm.startSubRecord("FTEX");
             esm.writeT(it->mX);
             esm.writeT(it->mY);
-            esm.write(&it->mImageData[0], it->mImageData.size());
+            esm.write(it->mImageData.data(), it->mImageData.size());
             esm.endRecord("FTEX");
         }
     }