Merge pull request #1063 from paulromano/find-cell-bugfix

Make sure find_cell returns false when no cell is found

src/geometry.cpp

@@ -243,6 +243,8 @@ find_cell(Particle* p, int search_surf) {
       return find_cell(p, 0);
     }
   }
+
+  return found;
 }
 
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