[process] fix title_latex setter

est/core/process/process.py

@@ -68,6 +68,7 @@ class _NexusSpectrumDef:
         self.axes = axes
         self.auxiliary_signals = auxiliary_signals
         self.title = title
+        self.title_latex = title_latex
 
     @property
     def signal(self):
@@ -124,6 +125,13 @@ class _NexusSpectrumDef:
     def title_latex(self):
         return self.__title_latex
 
+    @title_latex.setter
+    def title_latex(self, title):
+        if not isinstance(title, (str, type(None))):
+            raise TypeError("`title` should be an instance of str or None")
+        else:
+            self.__title_latex = title
+
 
 class _NexusDatasetDef:
     """Util function to define a Nexus plot"""