Issue #30 and #29, and a suggestion for ease of use. (#31)

* Segfault fixed when SideBar has no child.

* Button: Make ButtonStyle::PLAIN the default style; Tab Frame: Fix for not switching to a view if the previous view was nullptr.

* Move the comment above the if statement.

library/include/borealis/button.hpp

@@ -58,7 +58,7 @@ class Button : public View
     float cornerRadiusOverride = 0;
 
   public:
-    Button(ButtonStyle style);
+    Button(ButtonStyle style = ButtonStyle::PLAIN);
     ~Button();
 
     void draw(NVGcontext* vg, int x, int y, unsigned width, unsigned height, Style* style, FrameContext* ctx) override;

library/lib/sidebar.cpp

@@ -41,8 +41,11 @@ View* Sidebar::getDefaultFocus()
     if (this->lastFocus >= this->children.size())
         this->lastFocus = 0;
 
+    View* toFocus{ nullptr };
     // Try to focus last focused one
-    View* toFocus = this->children[this->lastFocus]->view->getDefaultFocus();
+    if(this->children.size() != 0)
+        toFocus = this->children[this->lastFocus]->view->getDefaultFocus();
+
     if (toFocus)
         return toFocus;
 

library/lib/tab_frame.cpp

@@ -64,11 +64,9 @@ void TabFrame::switchToView(View* view)
         this->layout->removeView(1, false);
     }
 
-    if (view != nullptr)
-    {
-        this->layout->addView(view, true, true); // addView() calls willAppear()
-        this->rightPane = view;
-    }
+    this->rightPane = view;
+    if (this->rightPane != nullptr)
+        this->layout->addView(this->rightPane, true, true); // addView() calls willAppear()
 }
 
 void TabFrame::addTab(std::string label, View* view)