check that compiler name is not blank or empty

pep8

mesonbuild/envconfig.py

@@ -341,8 +341,8 @@ This is probably wrong, it should always point to the native compiler.''' % evar
             if command is not None:
                 command = shlex.split(command)
 
-        # Do not return empty string entries
-        if command is not None and len(command) == 0:
+        # Do not return empty or blank string entries
+        if command is not None and (len(command) == 0 or len(command[0].strip()) == 0):
             return None
         return command