Fix editing of single rebar object

Problem:
Unable to set OffsetStart value to greater than (size of structure
object along direction of expansion of rebars)/2 for single rebar object

Solution:
Drop check if(OffsetStart + OffsetEnd > size), when there is only one
rebar object.

src/Mod/Arch/ArchRebar.py

@@ -355,8 +355,9 @@ class _Rebar(ArchComponent.Component):
             if obj.CustomSpacing:
                 spacinglist = strprocessOfCustomSpacing(obj.CustomSpacing)
                 influenceArea = sum(spacinglist) - spacinglist[0] / 2 - spacinglist[-1] / 2
-        if (obj.OffsetStart.Value + obj.OffsetEnd.Value) > size:
-            return
+        if obj.Amount != 1:
+            if (obj.OffsetStart.Value + obj.OffsetEnd.Value) > size:
+                return
         # all tests ok!
         if hasattr(obj, "Length"):
             length = getLengthOfRebar(obj)