Simplify ResizingTextEdit::isFirstWord to avoid invalid QString index warnings

CHANGELOG.md

@@ -30,6 +30,7 @@
 - Bugfix: Fixed some channels still not loading in rare cases. (#3219)
 - Bugfix: Fixed a bug with usernames or emotes completing from the wrong position. (#3229)
 - Bugfix: Fixed second chatterino icon appearing in the dock when restarting on a crash in macOS. (#3268)
+- Bugfix: Fixed `QCharRef with an index pointing outside the valid range of a QString` warning that was emitted on every Tab press. (#3234)
 - Dev: Renamed CMake's build option `USE_SYSTEM_QT5KEYCHAIN` to `USE_SYSTEM_QTKEYCHAIN`. (#3103)
 - Dev: Add benchmarks that can be compiled with the `BUILD_BENCHMARKS` CMake flag. Off by default. (#3038)
 

src/widgets/helper/ResizingTextEdit.cpp

@@ -42,14 +42,8 @@ bool ResizingTextEdit::hasHeightForWidth() const
 bool ResizingTextEdit::isFirstWord() const
 {
     QString plainText = this->toPlainText();
-    for (int i = this->textCursor().position(); i >= 0; i--)
-    {
-        if (plainText[i] == ' ')
-        {
-            return false;
-        }
-    }
-    return true;
+    QString portionBeforeCursor = plainText.left(this->textCursor().position());
+    return !portionBeforeCursor.contains(' ');
 };
 
 int ResizingTextEdit::heightForWidth(int) const