propagate z_index from MathTex to TexSymbol

Author: behackl

manim/mobject/svg/tex_mobject.py

@@ -329,7 +329,7 @@ def get_tex_string(self):
     def path_string_to_mobject(self, path_string):
         # Overwrite superclass default to use
         # specialized path_string mobject
-        return TexSymbol(path_string)
+        return TexSymbol(path_string, z_index=self.z_index)
 
     def organize_submobjects_left_to_right(self):
         self.sort(lambda p: p[0])
@@ -417,6 +417,7 @@ def break_up_by_substrings(self):
                 tex_string,
                 tex_environment=self.tex_environment,
                 tex_template=self.tex_template,
+                z_index=self.z_index,
             )
             num_submobs = len(sub_tex_mob.submobjects)
             new_index = curr_index + num_submobs