Merge pull request Ericsson#4698 from alfonsoespinosa/diagtool-missing-warning-not-crashing

[fix] diagtool get_warnings() returns if binary missing

Author: bruntib

analyzer/codechecker_analyzer/analyzers/clangtidy/analyzer.py

@@ -173,11 +173,12 @@ def get_warnings():
     Returns list of warning flags by using diagtool.
     """
     diagtool_bin = get_diagtool_bin()
-    environment = analyzer_context.get_context().get_env_for_bin(diagtool_bin)
 
     if not diagtool_bin:
         return []
 
+    environment = analyzer_context.get_context().get_env_for_bin(diagtool_bin)
+
     try:
         result = subprocess.check_output(
             [diagtool_bin, 'tree'],