Cast empty optional options in constructor

To remove the typescript errors:
```
Property 'xxx' does not exist on type '{}'
```

src/ol/PluggableMap.js

@@ -615,7 +615,7 @@ class PluggableMap extends BaseObject {
     if (!this.frameState_) {
       return;
     }
-    const options = opt_options || {};
+    const options = opt_options || /** @type {module:ol/PluggableMap~AtPixelOptions} */ ({});
     const hitTolerance = options.hitTolerance !== undefined ?
       opt_options.hitTolerance * this.frameState_.pixelRatio : 0;
     const layerFilter = options.layerFilter || TRUE;

src/ol/source/ImageArcGISRest.js

@@ -57,7 +57,7 @@ class ImageArcGISRest extends ImageSource {
    */
   constructor(opt_options) {
 
-    const options = opt_options || {};
+    const options = opt_options || /** @type {module:ol/source/ImageArcGISRest~Options} */ ({});
 
     super({
       attributions: options.attributions,

src/ol/source/ImageWMS.js

@@ -64,7 +64,7 @@ class ImageWMS extends ImageSource {
    */
   constructor(opt_options) {
 
-    const options = opt_options || {};
+    const options = opt_options || /** @type {module:ol/source/ImageWMS~Options} */ ({});
 
     super({
       attributions: options.attributions,

src/ol/source/TileWMS.js

@@ -82,7 +82,7 @@ class TileWMS extends TileImage {
    */
   constructor(opt_options) {
 
-    const options = opt_options || {};
+    const options = opt_options || /** @type {module:ol/source/TileWMS~Options} */ ({});
 
     const params = options.params || {};
 

src/ol/style/Circle.js

@@ -27,7 +27,7 @@ class CircleStyle extends RegularShape {
    */
   constructor(opt_options) {
 
-    const options = opt_options || {};
+    const options = opt_options || /** @type {module:ol/style/Circle~Options} */ ({});
 
     super({
       points: Infinity,