Minor convenience issue that I wanted done with.

Docs/Changelog_sm5.txt

@@ -12,6 +12,9 @@ StepMania 5.0 $next | 20111xxx
 ----------
 * [ScreenEdit] Restore using F9 and F10 to adjust stops by a fixed amount.
   Sorry for the delay in this. [Wolfman2000]
+* [ScreenEdit] Minor convenience. If you attempt to create a negative stop
+  segment from scratch, it does not create, and you are not requested to
+  save on exit, for there is nothing to save. [Wolfman2000]
 
 2011/11/25
 ----------

src/ScreenEdit.cpp

@@ -1908,6 +1908,8 @@ void ScreenEdit::InputEdit( const InputEventPlus &input, EditButton EditB )
 			{
 				if( fDelta > 0 )
 					timing.AddSegment( StopSegment(GetRow(), fDelta) );
+				else
+					break;
 			}
 			else
 			{