ASAN fixes (#1147)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

include/mbgl/gfx/vertex_attribute.hpp

@@ -50,7 +50,7 @@ public:
           items(std::move(other.items)) {}
 
 public:
-    ~VertexAttribute() = default;
+    virtual ~VertexAttribute() = default;
 
     int getIndex() const { return index; }
     void setIndex(int value) { index = value; }

include/mbgl/gl/vertex_attribute_gl.hpp

@@ -22,6 +22,9 @@ private:
         : VertexAttribute(std::move(other)),
           glType(other.glType) {}
 
+public:
+    virtual ~VertexAttributeGL() = default;
+
 public:
     platform::GLenum getGLType() const { return glType; }
     void setGLType(platform::GLenum value);