Only get pc for r2 when the process is running (#584)

pwndbg/commands/radare2.py

@@ -25,10 +25,11 @@ def r2(arguments, no_seek=False):
 
     # Build up the command line to run
     cmd = ['radare2', filename]
+    if pwndbg.proc.alive:
         addr = pwndbg.regs.pc
         if pwndbg.elf.get_elf_info(filename).is_pie:
             addr -= pwndbg.elf.exe().address
-    if not no_seek and pwndbg.proc.alive:
+        if not no_seek:
             cmd.extend(['-s', hex(addr)])
     cmd += arguments