STY: fix anal PEP8 complaint

PEP8 didn't like the indent, and my editor does, so change the syntax to
make PEP8 and my editor agree.

Author: matthew-brett

nibabel/dataobj_images.py

@@ -340,9 +340,10 @@ def get_fdata(self, caching='fill', dtype=np.float64):
         dtype = np.dtype(dtype)
         if not issubclass(dtype.type, np.inexact):
             raise ValueError('{} should be floating point type'.format(dtype))
-        if (self._fdata_cache is not None and
-            self._fdata_cache.dtype.type == dtype.type):
-            return self._fdata_cache
+        # Return cache if cache present and of correct dtype.
+        if self._fdata_cache is not None:
+            if self._fdata_cache.dtype.type == dtype.type:
+                return self._fdata_cache
         data = np.asanyarray(self._dataobj).astype(dtype)
         if caching == 'fill':
             self._fdata_cache = data