Fix: Window location code

This bug happens when additional plot stacks get allocated when there is enough
room in the terminal.
An integer division rounding leads to some location to be skipped.

src/interface_layout_selection.c

@@ -165,12 +165,12 @@ void compute_sizes_from_layout(
   if (*num_plots == 0) {
     *plot_positions = NULL;
   } else {
-    *plot_positions = malloc(*num_plots * sizeof(**plot_positions));
+    *plot_positions = calloc(*num_plots, sizeof(**plot_positions));
     *plot_types = preferred_plot_type;
     unsigned rows_per_stack = rows_left / num_plot_stacks;
     if (rows_per_stack > 23)
       rows_per_stack = 23;
-    unsigned plot_per_row = *num_plots / num_plot_stacks;
+    unsigned plot_per_row = (*num_plots + (*num_plots % num_plot_stacks)) / num_plot_stacks;
     unsigned num_plot_done = 0;
     unsigned currentPosX = 0, currentPosY = rows_for_header;
     for (unsigned i = 0; i < num_plot_stacks; ++i) {