when backspacing, needs to keep modified line status

if the current line is modified and backspace is used to combine the
line with the previous 'blank' line, the modified line needs to follow
the current line (in other words decremented)

only if the previous line is not empty, should the modified line be
reset, which will be set once the backspace is processed and the cursor
is moved to the previous line (when the previous line is blank, the
ignore change flag is used)

editbox.cpp

@@ -148,14 +148,22 @@ void EditBox::keyPressEvent(QKeyEvent *event)
 					{
 						// previous line blank, mark it for deletion instead
 						line--;
+						if (m_lineModified >= 0)  // current line modified?
+						{
+							// adjust modified line to its new line
+							m_lineModified--;
+						}
 						m_ignoreChange = true;
 					}
+					else
+					{
+						// line was deleted, do not report as changed
+						m_lineModified = -1;
+					}
 					// indicate line is about to be deleted
 					emit linesDeleted(line, 1);
-					// line was deleted, make sure it is not reported changed
-					m_lineModified = -1;
 
-					// is line is blank, combine won't modified previous line
+					// is line is blank, combine won't modify previous line
 					if (cursor.atBlockEnd())
 					{
 						// prevent backspace setting modified line