Remove useless check for null object with spread operator

js/src/dropdown/dropdown.js

@@ -341,7 +341,7 @@ class Dropdown {
   }
 
   _getPopperConfig() {
-    let popperConfig = {
+    const popperConfig = {
       placement: this._getPlacement(),
       modifiers: {
         offset: this._getOffset(),
@@ -361,16 +361,12 @@ class Dropdown {
       }
     }
 
-    if (this._config.popperConfig) {
-      popperConfig = {
+    return {
       ...popperConfig,
       ...this._config.popperConfig
     }
   }
 
-    return popperConfig
-  }
-
   // Static
 
   static dropdownInterface(element, config) {

js/src/tooltip/tooltip.js

@@ -483,17 +483,12 @@ class Tooltip {
       onUpdate: data => this._handlePopperPlacementChange(data)
     }
 
-    let resultConfig = defaultBsConfig
-    if (this.config.popperConfig) {
-      resultConfig = {
+    return {
       ...defaultBsConfig,
       ...this.config.popperConfig
     }
   }
 
-    return resultConfig
-  }
-
   _addAttachmentClass(attachment) {
     this.getTipElement().classList.add(`${CLASS_PREFIX}-${attachment}`)
   }