Fix processing of line immediately after # in properties file

Fixes gh-24158

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/OriginTrackedPropertiesLoader.java

@@ -168,8 +168,10 @@ class OriginTrackedPropertiesLoader {
 		result = result && readAndExpect(reader, reader::isHyphenCharacter);
 		result = result && readAndExpect(reader, reader::isHyphenCharacter);
 		result = result && readAndExpect(reader, reader::isHyphenCharacter);
-		reader.read();
-		reader.skipWhitespace();
+		if (!reader.isEndOfLine()) {
+			reader.read();
+			reader.skipWhitespace();
+		}
 		return result && reader.isEndOfLine();
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/OriginTrackedPropertiesLoaderTests.java

@@ -293,6 +293,12 @@ class OriginTrackedPropertiesLoaderTests {
 		assertThat(this.documents.size()).isEqualTo(1);
 	}
 
+	@Test
+	void getPropertyAfterPoundCharacter() {
+		OriginTrackedValue value = getFromFirst("test-line-after-empty-pound");
+		assertThat(getValue(value)).isEqualTo("abc");
+	}
+
 	private OriginTrackedValue getFromFirst(String key) {
 		return this.documents.get(0).asMap().get(key);
 	}

spring-boot-project/spring-boot/src/test/resources/org/springframework/boot/env/test-properties.properties

@@ -43,3 +43,6 @@ test-iso8859-1-chars=
 
 test-with-trailing-space= trailing 
 test-with-escaped-trailing-space= trailing\ 
+
+#
+test-line-after-empty-pound=abc
\ No newline at end of file