LibGUI: Split InsertTextCommand undo/redo based on whitespace

Userland/Libraries/LibGUI/TextDocument.cpp

@@ -764,16 +764,22 @@ bool InsertTextCommand::merge_with(GUI::Command const& other)
 {
     if (!is<InsertTextCommand>(other))
         return false;
-    auto& typed_other = static_cast<InsertTextCommand const&>(other);
+
+    auto const& typed_other = static_cast<InsertTextCommand const&>(other);
+    if (typed_other.m_text.is_whitespace() && !m_text.is_whitespace())
+        return false; // Skip if other is whitespace while this is not
+
     if (m_range.end() != typed_other.m_range.start())
         return false;
     if (m_range.start().line() != m_range.end().line())
         return false;
+
     StringBuilder builder(m_text.length() + typed_other.m_text.length());
     builder.append(m_text);
     builder.append(typed_other.m_text);
     m_text = builder.to_string();
     m_range.set_end(typed_other.m_range.end());
+
     return true;
 }