Fix #108737: Python error in Property Editor search menu

Caused by 5ca65001ea (which was already patched with ae7c71ef09 and
fa5cc84a0a)

Getting the right modifier would still fail / throw errors when not done
from the modifier extra ops dropdown.
Only there,  a 'modifier' attribute is set for context (via
`uiLayoutSetContextPointer` in `modifier_ops_extra_draw`).

So now check if a 'modifier' attribute is set for context (and fallback
to using the active modifier instead).
This way, polling errors in F3 search are gone and you can actually
execute the operators which are also in modifier extra ops dropdown from
elsewhere (e.g. F3 search).

@@ -46,3 +46,3 @@
 def get_context_modifier(context):
     area = context.area
-    if (area is not None) and (area.type == 'PROPERTIES'):
+    # Context only has a 'modifier' attribute in the modifier extra ops dropdown