Fix regression in launching executables as command line arguments without full paths

kitty/tabs.py

@@ -293,6 +293,10 @@ class Tab:  # {{{
                 cmd = self.args.args or resolved_shell(self.opts)
         if check_for_suitability:
             old_exe = cmd[0]
+            if not os.path.isabs(old_exe):
+                import shutil
+                actual_exe = shutil.which(old_exe)
+                old_exe = actual_exe if actual_exe else os.path.abspath(old_exe)
             try:
                 is_executable = os.access(old_exe, os.X_OK)
             except OSError: