runner.go: Propagate panics back to the user.

This is a partial revert of 8a35bb92
"runner.go: Increase survivability of main processing loop", removing
the panic handler.

Although we want to avoid errors taking down the runner, we also
should make the user aware of problems when they happen. In the
future, we can restructure things so both parts are true.

llama/runner/runner.go

@@ -357,6 +357,14 @@ func (s *Server) processBatch(tokenBatch *llama.Batch, embedBatch *llama.Batch)
 			continue
 		}
 
+		// If an error occurred during the processing of a previous batch then we may have emptied the inputs
+		// without adding a new one. In this case, end the sequence rather than infinite looping.
+		if len(seq.inputs) == 0 {
+			slog.Error("removing sequence due to no input tokens", "index", seqIdx, "cache id", seq.cache.Id)
+			s.removeSequence(seqIdx, "error")
+			continue
+		}
+
 		// if past the num predict limit
 		if seq.numPredict > 0 && seq.numPredicted >= seq.numPredict {
 			s.removeSequence(seqIdx, "limit")