fix use-of-uninitialized-value in survive_kalman_tracker_stats

integration_variance[16] is stack-allocated but variance_tracker_calc()
may not write all elements when the tracker had zero observations
(counts == 0 or variance.size == 0). The uninitialized array is then
read by SV_VERBOSE via LINMATH_VEC7_EXPAND / LINMATH_VEC6_EXPAND.

Found by MSan when running test_replays.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 2 people

src/survive_kalman_tracker.c

@@ -1485,7 +1485,7 @@ void survive_kalman_tracker_stats(SurviveKalmanTracker *tracker) {
 	SV_VERBOSE(5, "\t%-32s " Point19_format, "Mean reported variance", LINMATH_VEC19_EXPAND(var));
 	scalend(var, tracker->stats.dropped_var, 1. / tracker->stats.reported_poses, SURVIVE_MODEL_MAX_STATE_CNT);
 	SV_VERBOSE(5, "\t%-32s " Point19_format, "Mean dropped variance", LINMATH_VEC19_EXPAND(var));
-	FLT integration_variance[16];
+	FLT integration_variance[16] = {0};
 	variance_tracker_calc(&tracker->pose_variance, integration_variance);
 	SV_VERBOSE(5, "\t%-32s %e (%7u integrations, %7.3fhz) " Point7_format, "Obs error",
 			   tracker->stats.obs_total_error / (FLT)tracker->stats.obs_count, (unsigned)tracker->stats.obs_count,