More robust add/remove condition checks (#1840)

Author: Pessimistress

examples/terrain/src/app.tsx

@@ -29,6 +29,7 @@ export default function App() {
           bearing: 80,
           pitch: 80
         }}
+        maxPitch={85}
         mapStyle="mapbox://styles/mapbox/satellite-v9"
         mapboxAccessToken={TOKEN}
         terrain={{source: 'mapbox-dem', exaggeration: 1.5}}

src/components/layer.ts

@@ -61,7 +61,7 @@ function updateLayer(map: MapboxMap, id: string, props: LayerProps, prevProps: L
 
 function createLayer(map: MapboxMap, id: string, props: LayerProps) {
   // @ts-ignore
-  if (map.style && map.style._loaded && map.getSource(props.source)) {
+  if (map.style && map.style._loaded && (!('source' in props) || map.getSource(props.source))) {
     const options: LayerProps = {...props, id};
     delete options.beforeId;
 
@@ -90,7 +90,7 @@ function Layer(props: LayerProps) {
       return () => {
         map.off('styledata', forceUpdate);
         // @ts-ignore
-        if (map.style && map.style._loaded) {
+        if (map.style && map.style._loaded && map.getLayer(id)) {
           map.removeLayer(id);
         }
       };