Bugfix for libheif detection

When the LIBHEIF_LIBRARIES refers to targets (like happening when conan packaging provides the targets), an empty string from
get_filename_component will fail as it is not counted as an argument if used without quotes.

Author: irieger

src/heif.imageio/CMakeLists.txt

@@ -8,7 +8,7 @@ if (Libheif_FOUND)
     set (_static_libraries_found 0)
     foreach (_libeheif_library IN LISTS LIBHEIF_LIBRARIES)
         get_filename_component (_ext ${_libeheif_library} LAST_EXT)
-        list (FIND _static_suffixes ${_ext} _index)
+        list (FIND _static_suffixes "${_ext}" _index)
         if (${_index} GREATER -1)
             MATH (EXPR _static_libraries_found "${_static_libraries_found}+1")
         endif()