fix build store range check (#437)

* fix range check for blob store fetch
* don't try to parse blockdesriptions if empty result is returned
* add range to log when fetching blob range fails

1 files changed, 9 insertions, 2 deletions

diff --git a/src/zen/cmds/builds_cmd.cpp b/src/zen/cmds/builds_cmd.cpp
index abb4bfe0c..706fdf9ba 100644
--- a/src/zen/cmds/builds_cmd.cpp
+++ b/src/zen/cmds/builds_cmd.cpp
@@ -3503,7 +3503,11 @@ namespace {
 				{
 					ZEN_TRACE_CPU("FindBlocks");
 					Stopwatch KnownBlocksTimer;
-					Result.KnownBlocks = ParseChunkBlockDescriptionList(Storage.BuildStorage->FindBlocks(BuildId, FindBlockMaxCount));
+					CbObject  BlockDescriptionList = Storage.BuildStorage->FindBlocks(BuildId, FindBlockMaxCount);
+					if (BlockDescriptionList)
+					{
+						Result.KnownBlocks = ParseChunkBlockDescriptionList(BlockDescriptionList);
+					}
 					FindBlocksStats.FindBlockTimeMS = KnownBlocksTimer.GetElapsedTimeMs();
 					FindBlocksStats.FoundBlockCount = Result.KnownBlocks.size();
 					Result.FindBlocksTimeMs			= KnownBlocksTimer.GetElapsedTimeMs();
@@ -7440,7 +7444,10 @@ namespace {
 							}
 							if (!BlockBuffer)
 							{
-								throw std::runtime_error(fmt::format("Block {} is missing", BlockDescription.BlockHash));
+								throw std::runtime_error(fmt::format("Block {} is missing when fetching range {} -> {}",
+																	 BlockDescription.BlockHash,
+																	 BlockRange.RangeStart,
+																	 BlockRange.RangeStart + BlockRange.RangeLength));
 							}
 							if (!AbortFlag)
 							{