T94008, T94292

When importing a PDB file, the user has to be in the 'OBJECT' mode. With the changes
in the code, this mode is automatically set before the PDB import. No error message
should appear when the 'EDIT' mode is still active.

io_mesh_atomic/pdb_gui.py

@@ -203,6 +203,9 @@ class IMPORT_OT_pdb(Operator, ImportHelper):
 
 
     def execute(self, context):
+        # To be on the safe side, we switch to the 'OBJECT' mode.
+        bpy.ops.object.mode_set(mode='OBJECT', toggle=False)
+
         # This is in order to solve this strange 'relative path' thing.
         filepath_pdb = bpy.path.abspath(self.filepath)