bitbake: data_smart: Fix unneeded variable manipulation

If was pointed out that if we have:

XXX = " A"
XXX_remove_inactive-override = "YY"

then XXX can become "A" and the leading space can be removed. This is because
the remove override code changes the variable value even when there is no
removals active. In the process it dirties the cache.

We don't really need to do this so tweak the code accordingly.

(Bitbake rev: 2bc4d35fb32defc59cd6ed1fc87e35924c201a5c)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -784,13 +784,14 @@ class DataSmart(MutableMapping):
                 if match:
                     removes.extend(self.expand(r).split())
 
-            filtered = filter(lambda v: v not in removes,
-                              value.split())
-            value = " ".join(filtered)
-            if expand and var in self.expand_cache:
-                 # We need to ensure the expand cache has the correct value
-                 # flag == "_content" here
-                self.expand_cache[var].value = value
+            if removes:
+                filtered = filter(lambda v: v not in removes,
+                                  value.split())
+                value = " ".join(filtered)
+                if expand and var in self.expand_cache:
+                    # We need to ensure the expand cache has the correct value
+                    # flag == "_content" here
+                    self.expand_cache[var].value = value
         return value
 
     def delVarFlag(self, var, flag, **loginfo):