Reindent do_bedtemp and fix broken code path

The if f >= 0 could be have been accessed even though f had not been
assigned (if float(l) failed)

pronsole.py

@@ -1121,6 +1121,7 @@ class pronsole(cmd.Cmd):
             return [i for i in self.temps.keys() if i.startswith(text)]
 
     def do_bedtemp(self, l):
+        f = None
         try:
             l = l.lower().replace(", ",".")
             for i in self.bedtemps.keys():
@@ -1128,9 +1129,9 @@ class pronsole(cmd.Cmd):
             f = float(l)
         except:
             self.logError(_("You must enter a temperature."))
-            if f>=0:
+        if f is not None and f >= 0:
             if self.p.online:
-                    self.p.send_now("M140 S"+l)
+                self.p.send_now("M140 S" + l)
                 self.log(_("Setting bed temperature to %s degrees Celsius.") % f)
             else:
                 self.logError(_("Printer is not online."))