Draft: Fix error when deleting first digit of input

Fixes #13150.

src/Mod/Draft/DraftGui.py

@@ -1095,10 +1095,13 @@ class DraftToolBar:
         treated as shortcuts
         """
 
-        if txt == "" or txt[0] in "0123456789.,-":
+        if txt == "":
             self.updateSnapper()
-            if txt[0] in "0123456789.,-":
-                self.setMouseMode(False)
+            return
+
+        if txt[0] in "0123456789.,-":
+            self.updateSnapper()
+            self.setMouseMode(False)
             return
 
         txt = txt[0].upper()