layers: Revert "Prevent layer calls with null ..."

Incomplete solution, with new null derefence side affects.

This reverts commit 9652bf9ce450f79ccf69de911a9744a8d7ed6222.

Change-Id: I5530fd496d3495bc9863ddaf709b32c6f7b95329
diff --git a/scripts/threading_generator.py b/scripts/threading_generator.py
index 7475898..5cfb4d7 100644
--- a/scripts/threading_generator.py
+++ b/scripts/threading_generator.py
@@ -274,7 +274,7 @@
         self.newline()
         # record intercepted procedures
         write('// Map of all APIs to be intercepted by this layer', file=self.outFile)
-        write('static std::unordered_map<std::string, void*> name_to_funcptr_map = {', file=self.outFile)
+        write('static const std::unordered_map<std::string, void*> name_to_funcptr_map = {', file=self.outFile)
         write('\n'.join(self.intercepts), file=self.outFile)
         write('};\n', file=self.outFile)
         self.newline()