TextEditor: Fix unindent on backspace.

Task-number: QTCREATORBUG-15250
Change-Id: I4d19ad90098dc64f96b1aa7f728d8f30d05bff6d
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>

src/plugins/texteditor/tabsettings.cpp

@@ -229,7 +229,7 @@ int TabSettings::columnCountForText(const QString &text, int startColumn) const
 
 int TabSettings::spacesLeftFromPosition(const QString &text, int position)
 {
-    if (position >= text.size())
+    if (position > text.size())
         return 0;
     int i = position;
     while (i > 0) {