vulkan: fix canvas rendering

Sometimes canvas commands wouldn't get executed.
This was because when the window gets resized,
the command buffers would get recreated, and would thus
lose the recorded commands.

src/modules/graphics/vulkan/Texture.cpp

@@ -63,10 +63,10 @@ namespace love {
 						std::vector<uint8> defaultPixels;
 						defaultPixels.reserve(width * height * 4);
 						for (size_t i = 0; i < width * height; i++) {
-							// transparent white
-							defaultPixels.push_back(255);
-							defaultPixels.push_back(255);
-							defaultPixels.push_back(255);
+							// transparent black
+							defaultPixels.push_back(0);
+							defaultPixels.push_back(0);
+							defaultPixels.push_back(0);
 							defaultPixels.push_back(255);
 						}
 						Rect rect = { 0, 0, width, height };