Text: correctly propagate errors when delegating to *SingleData() APIs.

The AbstractFontConverter tests now all pass again.

doc/changelog.dox

@@ -188,6 +188,11 @@ See also:
 -   @ref Shaders::Phong wasn't normalizing normals coming from normal textures,
     which may have caused slight artifacts due to limited precision of 8-bit
     pixel formats
+-   @ref Text::AbstractFontConverter::exportFontToData() and
+    @ref Text::AbstractFontConverter::exportGlyphCacheToData() didn't correctly
+    propagate errors when delegating to
+    @ref Text::AbstractFontConverter::exportFontToSingleData() /
+    @ref Text::AbstractFontConverter::exportGlyphCacheToSingleData()
 
 @subsection changelog-latest-deprecated Deprecated APIs
 

src/Magnum/Text/AbstractFontConverter.cpp

@@ -103,7 +103,8 @@ std::vector<std::pair<std::string, Containers::Array<char>>> AbstractFontConvert
         "Text::AbstractFontConverter::exportFontToData(): feature advertised but not implemented", {});
 
     std::vector<std::pair<std::string, Containers::Array<char>>> out;
-    out.emplace_back(filename, doExportFontToSingleData(font, cache, characters));
+    Containers::Array<char> result = doExportFontToSingleData(font, cache, characters);
+    if(result) out.emplace_back(filename, std::move(result));
     return out;
 }
 
@@ -155,7 +156,8 @@ std::vector<std::pair<std::string, Containers::Array<char>>> AbstractFontConvert
         "Text::AbstractFontConverter::exportGlyphCacheToData(): feature advertised but not implemented", {});
 
     std::vector<std::pair<std::string, Containers::Array<char>>> out;
-    out.emplace_back(filename, doExportGlyphCacheToSingleData(cache));
+    Containers::Array<char> result = doExportGlyphCacheToSingleData(cache);
+    if(result) out.emplace_back(filename, std::move(result));
     return out;
 }