respect should_exit on linux as well

Also remove categorized days that had the deleted category.

src/work-calendar.cpp

@@ -485,6 +485,18 @@ void per_frame(){
 
                 ImGui::TableSetColumnIndex(3);
                 if (ImGui::Button("d")) {
+                    for (size_t j = 0; j < num_categorized_days; j++) {
+                        // Remove categorized days that have the to be deleted category
+                        if (categorized_days[j].category == i) {
+                            for (size_t k = j; k < num_categorized_days - 1; k++) categorized_days[k] = categorized_days[k + 1];
+                            num_categorized_days--;
+                            j--;
+                        }
+                        // Decrement the category index of all categorized days that have an index higher than the one to be removed
+                        if (categorized_days[j].category > i) categorized_days[j].category--;
+                    }
+                    // Remove the category
+                    for (size_t j = i; j < num_categories - 1; j++) categories[j] = categories[j + 1];
                     num_categories--;
                 }