fix: make INSTANA_CONFIG_PATH compatible to both trace disabling and stack trace

Signed-off-by: Varsha GS <varsha.gs@ibm.com>

Author: GSVarsha

src/instana/util/config.py

@@ -326,8 +326,9 @@ def get_disable_trace_configurations_from_yaml() -> Tuple[List[str], List[str]]:
     if not root_key:
         return [], []
 
-    tracing_disable_config = config_reader.data[root_key].get("disable", "")
-    return parse_span_disabling(tracing_disable_config)
+    if tracing_disable_config := config_reader.data[root_key].get("disable", None):
+        return parse_span_disabling(tracing_disable_config)
+    return [], []
 
 
 def get_disable_trace_configurations_from_local() -> Tuple[List[str], List[str]]: