Minor spacing issue fix.

Change-Id: I056354f0066e4912c2143798151e2c8e24b0f729

internal/ceres/trust_region_minimizer.cc

diff --git a/internal/ceres/trust_region_minimizer.cc b/internal/ceres/trust_region_minimizer.cc
index bb6c4a1..6030f95 100644
--- a/internal/ceres/trust_region_minimizer.cc
+++ b/internal/ceres/trust_region_minimizer.cc
@@ -359,7 +359,7 @@
         return;
       }
 
-      VLOG(2) << "old cost: " << cost << "new cost: " << new_cost;
+      VLOG(2) << "old cost: " << cost << " new cost: " << new_cost;
       iteration_summary.cost_change =  cost - new_cost;
       const double absolute_function_tolerance =
           options_.function_tolerance * cost;