Skip multiplication for layer type

The layer type is a string and should not be multiplied.

Originally, the multiplication worked fine, because the multiplier
was an integer of 1, and doing things like `'sample' * 1` results in
`'sample'` - just the string.

However, we changed the multiplier to a float in the type annotations
PR, and we can't multiply a float with a string, so we would get
an error.

This fixes the code so the layer type string does not get multiplied
at all.

Signed-off-by: Patrick Avery <patrick.avery@kitware.com>

Author: psavery

hexrdgui/pinhole_correction_editor.py

@@ -192,7 +192,10 @@ def correction_kwargs(self, v: dict[str, Any] | None) -> None:
         vp = v.copy()
         # These units are in mm, but we display in micrometers
         for key, value in v.items():
-            if key in ('num_phi_elements', 'absorption_length', 'layer_type'):
+            if key == 'layer_type':
+                # This is a string, not numeric. Skip conversion.
+                continue
+            elif key in ('num_phi_elements', 'absorption_length'):
                 multiplier = 1.0
             else:
                 multiplier = 1e3