Changed use of some Matrix.invert() to Matrix.invert_safe() to preven…

…t crashes:

- This is used when the child transformations need to be calculated in the parent space.
- This prevent crashes when the parent scale is 0.
- The solution is not perfect. Calculating transformations in a space scaled to 0 is meaningless, the transformations won't be visible anyway. The child transformations shouldn't really be exported at all in that case. This will cause imperfect results during interpolation from 0 scaled frame to the next frame.

mcblend/operator_func/common.py

@@ -302,7 +302,13 @@ def get_local_matrix(
         if normalize:
             p_matrix.normalize()
             c_matrix.normalize()
-        return p_matrix.inverted() @ c_matrix
+        # The inver_safe() function is used to avoid errors when the parent
+        # matrix is scaled to zero on some axis (which makes it non-invertible)
+        # It's not perfect becuase the child transformations will be incorrect
+        # but it prevents crashes and in theory the child transformations on
+        # that axis shouldn't be visible anyway (they are during interpolation
+        # between keyframes).
+        return p_matrix.inverted_safe() @ c_matrix
 
     def get_mcrotation(
             self, other: Optional[McblendObject] = None
@@ -323,7 +329,7 @@ def local_rotation(
             Returns Euler rotation of a child matrix in relation to parent matrix
             '''
             child_q = child_matrix.normalized().to_quaternion()
-            parent_q = parent_matrix.inverted().normalized().to_quaternion()
+            parent_q = parent_matrix.inverted_safe().normalized().to_quaternion()
             return (parent_q @ child_q).to_euler('XZY')
 
         if other is not None: