Fix crash if Python frame filename is NULL

For Python functions created at runtime, there is no associated
filename, in which case the filename can be NULL. There was code in
ctau_impl.c that assumed the filename was not NULL. This fixes the issue
by using the empty string for the filename if the filename is NULL.


Former-commit-id: 32e2abe04bd4029bbc9e2e67ee0c31efbf5a832b

src/Profile/ctau_impl.c

@@ -444,17 +444,19 @@ static ProfilerEntry *newProfilerEntry(ProfilerObject *pObj, void *key, PyObject
       PyCodeObject * codeObj = PyFrame_GetCode(frame);
       co_name = PyString_AsString(codeObj->co_name);
       co_filename = PyString_AsString(codeObj->co_filename);
+      if(co_filename == NULL) {
+        co_filename = "";
+      }
       while (strchr(co_filename,'/')) {
-	co_filename = strchr(co_filename,'/')+1;
+	    co_filename = strchr(co_filename,'/')+1;
       }
       co_firstlineno = codeObj->co_firstlineno;
       sprintf (routine,"%s [{%s}{%d}]", co_name, co_filename, co_firstlineno);
       if (strcmp(co_filename,"<string>") != 0) { // suppress "? <string>"
-	TAU_PROFILER_CREATE(handle, routine, "", TAU_PYTHON);
+	    TAU_PROFILER_CREATE(handle, routine, "", TAU_PYTHON);
       }
   } else {
     if (strcmp (cname, "profileTimer") && strcmp (cname, "start") && strcmp (cname, "stop") && strcmp (cname, "disable")) {
-/*       sprintf (routine,"C [%s]", cname); */
       sprintf (routine,"%s", cname);
       TAU_PROFILER_CREATE(handle, routine, "", TAU_PYTHON);
     }