Examples: initializing float + missing comment.

examples/opengl_example/main.cpp

@@ -42,7 +42,7 @@ int main(int, char**)
         // 1. Show a simple window
         // Tip: if we don't call ImGui::Begin()/ImGui::End() the widgets appears in a window automatically called "Debug"
         {
-            static float f;
+            static float f = 0.0f;
             ImGui::Text("Hello, world!");
             ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
             ImGui::ColorEdit3("clear color", (float*)&clear_color);