Fix false positives from spellcheck checks

For some reason, this specific sentence results in a non-nil diff of lenght > 0. The previous approach of checking if
the diff was nil resulted in a false positive, which is avoided by basing the check on the length of the diff.

Author: per1234

Diff for: check/checkfunctions/library.go

@@ -1281,7 +1281,7 @@ func spellCheckLibraryPropertiesFieldValue(fieldName string) (result checkresult
 	}
 
 	replaced, diff := checkdata.MisspelledWordsReplacer().Replace(fieldValue)
-	if diff != nil {
+	if len(diff) > 0 {
 		return checkresult.Fail, replaced
 	}
 

Diff for: check/checkfunctions/library_test.go

@@ -264,6 +264,7 @@ func TestLibraryPropertiesSentenceFieldSpellCheck(t *testing.T) {
 		{"Unable to load", "InvalidLibraryProperties", checkresult.NotRun, ""},
 		{"Not defined", "MissingFields", checkresult.NotRun, ""},
 		{"Misspelled word", "MisspelledSentenceParagraphValue", checkresult.Fail, "^grill broccoli now$"},
+		{"Non-nil diff but no typos", "SpuriousMisspelledSentenceParagraphValue", checkresult.Pass, ""},
 		{"Correct spelling", "Recursive", checkresult.Pass, ""},
 	}
 
@@ -275,6 +276,7 @@ func TestLibraryPropertiesParagraphFieldSpellCheck(t *testing.T) {
 		{"Unable to load", "InvalidLibraryProperties", checkresult.NotRun, ""},
 		{"Not defined", "MissingFields", checkresult.NotRun, ""},
 		{"Misspelled word", "MisspelledSentenceParagraphValue", checkresult.Fail, "^There is a zebra$"},
+		{"Non-nil diff but no typos", "SpuriousMisspelledSentenceParagraphValue", checkresult.Pass, ""},
 		{"Correct spelling", "Recursive", checkresult.Pass, ""},
 	}
 

Diff for: check/checkfunctions/testdata/libraries/SpuriousMisspelledSentenceParagraphValue/library.properties

@@ -0,0 +1,9 @@
+name=SpuriousMisspelledSentenceParagraphValue
+version=1.0.0
+author=Cristian Maglie <[email protected]>, Pippo Pluto <[email protected]>
+maintainer=Cristian Maglie <[email protected]>
+sentence=Minimal bit bang send serial 115200 or 38400 baud for 1 MHz or 230400 baud for 16 MHz clock. Perfect
+paragraph=Minimal bit bang send serial 115200 or 38400 baud for 1 MHz or 230400 baud for 16 MHz clock. Perfect
+category=Communication
+url=http://example.com/
+architectures=avr