core: fix bug when starting path at chunk transition

We sometimes looked for a chunk that was
just outside of the path, and didn't find
it in the block path

Author: eckter

core/src/main/java/fr/sncf/osrd/standalone_sim/ScheduleMetadataExtractor.kt

@@ -573,8 +573,12 @@ fun trainPathBlockOffset(
     blockPath: StaticIdxList<Block>,
     chunkPath: ChunkPath
 ): Distance {
-    val firstChunk = chunkPath.chunks[0]
+    var firstChunk = chunkPath.chunks[0]
     var prevChunksLength = 0.meters
+    if (infra.getTrackChunkLength(firstChunk.value) == chunkPath.beginOffset) {
+        firstChunk = chunkPath.chunks[1]
+        prevChunksLength = -chunkPath.beginOffset.distance
+    }
     for (block in blockPath) {
         for (zonePath in blockInfra.getBlockPath(block)) {
             for (dirChunk in infra.getZonePathChunks(zonePath)) {