[RPP] check for negative entry index before processing initiator data

The check for -1 value is moved early in the processing, to ensure the
data is cleared up and not prevented due to early returns.

Fixed: 408140272
Change-Id: Icbf4f88403b0e7642e311ff810133bfa34329238
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6429725
Commit-Queue: Andres Olivares <andoli@chromium.org>
Auto-Submit: Andres Olivares <andoli@chromium.org>
Reviewed-by: Alina Varkki <alinavarkki@chromium.org>

Author: and-oli

front_end/panels/timeline/TimelineFlameChartDataProvider.ts

@@ -1249,16 +1249,6 @@ export class TimelineFlameChartDataProvider extends Common.ObjectWrapper.ObjectW
     if (!this.timelineDataInternal) {
       return false;
     }
-    if (this.lastInitiatorEntry === entryIndex) {
-      if (this.lastInitiatorsData) {
-        this.timelineDataInternal.initiatorsData = this.lastInitiatorsData;
-      }
-      return false;
-    }
-    if (!this.compatibilityTracksAppender) {
-      return false;
-    }
-
     // Remove all previously assigned decorations indicating that the flow event entries are hidden
     const previousInitiatorsDataLength = this.timelineDataInternal.initiatorsData.length;
     // |entryIndex| equals -1 means there is no entry selected, just clear the
@@ -1274,6 +1264,15 @@ export class TimelineFlameChartDataProvider extends Common.ObjectWrapper.ObjectW
       this.timelineDataInternal.resetFlowData();
       return true;
     }
+    if (this.lastInitiatorEntry === entryIndex) {
+      if (this.lastInitiatorsData) {
+        this.timelineDataInternal.initiatorsData = this.lastInitiatorsData;
+      }
+      return false;
+    }
+    if (!this.compatibilityTracksAppender) {
+      return false;
+    }
 
     const entryType = this.#entryTypeForIndex(entryIndex);
     if (entryType !== EntryType.TRACK_APPENDER) {