Improve search popup window titles (#2268)

Adds special cases for /whispers, /mentions and empty tabs, and an apostrophe in the titles.

Co-authored-by: Paweł <zneix@zneix.eu>

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Major: Added "Channel Filters". See https://wiki.chatterino.com/Filters/ for how they work or how to configure them. (#1748, #2083, #2090, #2200)
 - Major: Added Streamer Mode configuration (under `Settings -> General`), where you can select which features of Chatterino should behave differently when you are in Streamer Mode. (#2001)
+- Minor: Improved search popup window titles. (#2268)
 - Minor: Made "#channel" in `/mentions` tab a clickable link which takes you to the channel that you were mentioned in. (#2220)
 - Minor: Added a keyboard shortcut (Ctrl+F5) for "Reconnect" (#2215)
 - Minor: Made `Try to find usernames without @ prefix` option still resolve usernames when special characters (commas, dots, (semi)colons, exclamation mark, question mark) are appended to them. (#2212)

src/widgets/helper/SearchPopup.cpp

@@ -81,7 +81,25 @@ void SearchPopup::setChannel(const ChannelPtr &channel)
 
 void SearchPopup::updateWindowTitle()
 {
-    this->setWindowTitle("Searching in " + this->channelName_ + "s history");
+    QString historyName;
+
+    if (this->channelName_ == "/whispers")
+    {
+        historyName = "whispers";
+    }
+    else if (this->channelName_ == "/mentions")
+    {
+        historyName = "mentions";
+    }
+    else if (this->channelName_.isEmpty())
+    {
+        historyName = "<empty>'s";
+    }
+    else
+    {
+        historyName = QString("%1's").arg(this->channelName_);
+    }
+    this->setWindowTitle("Searching in " + historyName + " history");
 }
 
 void SearchPopup::search()