fixed uv missing in vertex shader of canvas.

drivers/gles3/shaders/canvas.glsl

@@ -145,6 +145,8 @@ void main() {
 
 #define extra_matrix extra_matrix_instance
 
+	//for compatibility with the fragment shader we need to use uv here
+	vec2 uv = uv_interp;
 	{
 		/* clang-format off */
 
@@ -153,6 +155,8 @@ VERTEX_SHADER_CODE
 		/* clang-format on */
 	}
 
+	uv_interp = uv;
+
 #ifdef USE_NINEPATCH
 
 	pixel_size_interp = abs(dst_rect.zw) * vertex;