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(),
@@ -361,14 +361,10 @@ class Dropdown {
       }
     }
 
-    if (this._config.popperConfig) {
-      popperConfig = {
-        ...popperConfig,
-        ...this._config.popperConfig
-      }
+    return {
+      ...popperConfig,
+      ...this._config.popperConfig
     }
-
-    return popperConfig
   }
 
   // Static

js/src/tooltip/tooltip.js

@@ -483,15 +483,10 @@ class Tooltip {
       onUpdate: data => this._handlePopperPlacementChange(data)
     }
 
-    let resultConfig = defaultBsConfig
-    if (this.config.popperConfig) {
-      resultConfig = {
-        ...defaultBsConfig,
-        ...this.config.popperConfig
-      }
+    return {
+      ...defaultBsConfig,
+      ...this.config.popperConfig
     }
-
-    return resultConfig
   }
 
   _addAttachmentClass(attachment) {