Prevent FPE in in task_overlap(). But that FPE should not be there in the first place...

src/task.c

@@ -266,6 +266,9 @@ float task_overlap(const struct task *restrict ta,
     if (tb->ci != NULL) size_union += tb->ci->hydro.count;
     if (tb->cj != NULL) size_union += tb->cj->hydro.count;
 
+    // MATTHIEU: This should not be necessary
+    if (size_union == 0) return 0.f;
+    
     /* Compute the intersection of the cell data. */
     const size_t size_intersect = task_cell_overlap_part(ta->ci, tb->ci) +
                                   task_cell_overlap_part(ta->ci, tb->cj) +